Try this:
len(substr(allt(padr(130.9898,20)), at(".", allt(padr(130.9898,20)) )+1 ) )

substitute your variable in place of the number in the expression above. The function "PADR() or PADL() or PADC()" converts the number as is rather than rounding or truncating like STR() does.

I hope this works.

Regards

Leonard