Batch volume with yeast starter

Hi guys
I use to brew a batchsize of 28 l (into fermentor) with dry yeast but now I want to add a 2 l starter. However the fermentor bucket cannot hold 30 l. Thus I tried to reduce the batch size to 26 l but then all calculated values of ABV, bitterness etc. goes up which the should not since the actual volume still is 26+2 =28 l. 
How can the starter be added and taken into account as "added water" thinning out the other ingredients i Beersmith?

Thanks in advance
Rgds Peter

When you get out of bed on the morning of brew day, take your starter off your stir plate and put it into the refrigerator.  This will cause the yeast to settle to the bottom.  About 30 minutes before it's time to pitch your yeast, take the starter out of the refrigerator and carefully decant the liquid off of the top of the yeast layer and let it sit covered with a piece of aluminum foil.  Then at pitching time, swirl it up good and pour it in.

The amount of extra liquid that is added to your batch size is insignificant doing it this way.

Hi Scott
Sounds like an obvious and great solution -never tried to brew with starters before
THANKS for your help on that one

Rgds
Peter