Thanks for the clarification. With that little peek into your world, I wonder if you could combine some of these or even all the D letters, but let's start small.

I imagine that R17 says something like
"we are sending you a check for (check_amt) and a credit of (credit_amt) and R18 says something like
"we are offering you a credit for (credit_amt)".

One way to make these one letter is to have something like (my syntax isn't perfect but it can get you started):
"we are sending you a check for (check_amt)
<if not blank> and a credit of (credit_amt)<end if>.

If you're not familiar with if statements, I recommend starting small by combining two letters. That would get you down to 15 to 20 letters and cut your work in half.