Hi,
replace the !A! and !B! with the fieldnames you want to use for the calculation.
If you want results without decimals use: round(!A!* !B! /10) and with decimal places: round(!A!* !B! /10.0)
10.0 could be any number you want to use, you just have to define the number of decimals, even if the field type is double and allows more decimals the script will not return more than what you have defined within the script.
Hope that helps!