Let me see if I can help you, if I understand your question.
You have a block that is 20" h by 19 3/4 w. You need it to be 22 1/2 " square. Right?
Remember with each seam, you lose 1/2" -- 1/4" per square/strip.
So, for top and bottom, you need 2 strips, 1 3/4" each. 20" + 1 3/4 + 1 3/4" = 23 1/2" minus 1" for seams = 22 1/2".
For each side, you need 2 strips, 1 7/8" each: 19 3/4" + 1 7/8" + 1 7/8" = 23 1/2" minus 1" for seams = 22 1/2.
I hope this is clear enough. Sometimes, I just make things more complicated than they need to be.