Oat meal stout

Hello,
I made this receipt for oatmeal stout, i m gonna craft it today or tomorrow. this is my first  receipt that made and first post  on this forum, so I want to help/advice me what should I add or remove from it. I will put picture of design(grains,hops and yeast) and mash process in beersmith2. Also i will be needed help about mash temperatures.
I have pot of 50L and after cooking get about 40-42L of beer.

In mash picture in description it says add 28L of water at 73 degres, and next column step temperature is 66.7 degres. What that mean step temperature,I  heat water at 73 and add it to mash?





And is how much grains goes per liter ?
And also  I never used orange peel and coriander how much is needed for my size of batch ?

I will appreciate every comment i get , thanks !

Just to alleviate any confusion, the picture you posted states the first step as adding 28 litres at 69.0 C.  If your grain temperature is correct and you have the specific heat for your mash tun correct, then adding the grains for the recipe to the mash water heated to 69C should give you a resultant temperature of 64C (the step temperature). Anything within a couple of tenths of target, IMHO, is fairly good.

Likewise for the sparge steps, although I really don't worry too much about the sparge temperature as long as it is not too hot and encourages the release of tannins from the grains.

In terms of your grains per liter, BeerSmith has already calculated that out based upon your grain bill.  You have 10 kgs of grain in the recipe and all get added to the mash. This would give you an initial water to grain ratio of 29 litres for 10 kgs of grain or 2.9 l/kg.

In terms of the amount of orange peel and coriander, I can't be of much help.  Much of the amount of coriander has to do with the freshness of quality of the spice.  I've used it in one repeat recipe and still have not been able to get it quite right.