As level - 77 is used for the variables that are not going to be modified through the execution you might be getting the error.
I believe using value clause (in working storage)should work for you.
Correct me.I will be happy to be cleare on this topic .So Correct me if i am wrong.
Low-value is NOT the "lowest legal value" in Cobol. "Low-value" is the
lowest possible value in the alphabetic colating sequence for a specific
machine, and applies only *alphabetic* fields. Numeric fields, on the
other hand, must be legal numeric *digits* in the aplhabetic set you are
using. The lowest legal *Number*(unsigned that is) is zero.