20 19 is what your looking for, I dont know why 2 values, a min max thing, as suggested in code tested with 145 144, its number of characters in the edit box.
You can make each edit box a different size like 4 3 for say 1-10 then 30 29 for a big string.
A further hint if you set a variable to say a number you can use that variable in the lst
(setq lst (list "Please enter values " "Enter client name: " 20 19 " " "Enter location: " 20 19 " " "Enter crop: " 20 19 "10" "Enter date code: " 20 19 " "
"Enter acres: " 20 19 " " "Enter plant count: " 20 19 " " "Enter application rate: " 20 19 "20"))
(if (= apprate nil)(setq apprate 20))
(setq lst (list "Please enter values " "Enter client name: " 20 19 " " "Enter location: " 20 19 " " "Enter crop: " 20 19 " " "Enter date code: " 20 19 " "
"Enter acres: " 20 19 " " "Enter plant count: " 20 19 " " "Enter application rate: " 20 19 (rtos apprate 2 0)))