In addition to what others have said I think I can add a little to the conversation. I've taken a look at your recipe and your settings and believe I have found something that should help clear things help. First, lets go through a little math.
first, the givens: Your recipe has 16.5 lbs of grain and you're mashing in at 1.25 qts of water per lb of grain (pretty standard). So, Beersmith looks at your settings and tells you that you need to mash in 16.5 * 1.25 = 20.625 qts for your first infusion. We simply divide that by four qts per gallon to get the 5.15625 gallons of water for your first infusion.
Now what we want to try and figure out is how much is going to end up in our brew kettle when it comes time to boil. Your mash settings have you doing a mash out with 11.55 qts (or 2.8875 gallons of water) that will be added in addition to the 5.15625 gallons already in there, for a grand total of 5.15625+2.8875=8.04375gallons of water put into the mash tun before any runnings. Of course we know that you won't get that much out because the grains will absorb a certain amount of that water that it isn't going to give back. I always use, and I believe BeerSmith uses the convention of the grain holding roughly its weight in water (I always check my math again BS and it always works out (less rounding errors) exactly the same with this convention). So, since we know a gallon of water weighs roughly 8.35 lbs we need to divide this number into our total grain weight of 16.5 lbs or 16.5/8.35=1.97 (the grain is holding onto 16.5 lbs of water) gallons of water absorbed into the grain.
So at this point, and I believe this is where your problem is, if you had no deadspace in your MLT and lost no water to evaporation or anything else you could expect your first runnings to be 8.04375 gallons infused - 1.9760479 gallons absorbed = 6.0677 gallons into the brew kettle. Of course, at this point you will need to sparge and BeerSmith calculates the sparge volume based on what you need to obtain your brew boil volume (I'm not sure why it tells you to top up, I have never needed to do that, Beer Smith calculates volumes so that you don't need to do that actually). In this case, based in your settings you need an additional .41 gallons which is what Beer Smith will tell you, you need to sparge with. Again, I zeroed out your deadspace amount (remember this is the wort that, on top of what's absorbed, just won't leave the MLT) and zeroed out your loss to evaporation etc and and the brewsheet matches the numbers I've given above. So, now, what's your problem.
I'm not sure why but you have 7 gallons of deadspace in your equipment setting!!!!! I have a hard time believing you are really losing those much wort, if you are then you may need to reconsider your MLT and how it's set up. My guess is that its just a typo or mistake that you forgot about or something simple like that. But, lets just say it's true and you really are losing this much wort, If we go back to the numbers above and include the 7 gallons of deadspace what happens is we can take our 6.0677 gallons of expected first runnings and minus out the 7 gallons of deadspace which leaves us -.9323 in the hole. Since what you want is 6.47 gallons for your brew kettle Beer Smith then tells you to add 7.41 gallons of water. Since you only lose the 7 gallons to deadspace once, you end up with 7.41+-.9323 which equals 6.47 gallons for your brew boil volume.
Now, having said all of that, what I don't understand is why BeerSmith is telling you to add an addition 4.94 gallons (2.47 gallons twice)? That one has me stumped and to be quite honest, according to my understanding of the numbers BeerSmith should not be telling you to do that. Based on your settings, it should only be telling you to add the one sparge round of 7.41 gallons. I'm wondering if the deadspace being so big that its larger than your first runnings confuses BS? I don't know the algorithms BS uses but that would be my guess.
In summary: If you understand how much water should be absorbed, plus how much you should lose to things like deadspace you really don't need BS to calculate this stuff. The math is easy enough that you can calculate it all yourself. The additional sparge rounds it's telling you to do is weird and I'm not sure why. I'd suggest SIGNIFICANTLY lowering your deadspace, I typically use .15 gallons and it has me pretty dialed in. Finally, make sure you are adjusting your hydrometer for the temp it's at when taking the measurement. Unless you've added water, your post boil gravity should never be less than your pre boil gravity.
Hope this helps,
$0.02