VOFM: value is enlarged in routine

Hello, everyone:

I meet a problem when I programming in routine for SD condition value:

the calculated result in the routine is enlarged automatically by system, for example, V1(10) * V2(10) = 100, but the result is 1000 in my routine, so it is enlarged by 10.

Why does system enlarges the result automatically?

What should I care when programming in such routine?

Thanks in advance!