DBPro converts datatypes on demand. If you do an integer operation (you have divide) the result will be an integer. The final integer will be converted to a float value when you assign it to a float variable. As you've discovered, this isn't what you usually want.
Integer operator Integer => Integer
Integer operator Float => Float
Float operator Float => Float
... Where operator can be *, /, +, -, ^, =
You have Integer divided by Integer, giving an Integer result. Convert one of those to a float value before doing the division and you'll get a float division and a float result:
Result# = (variable1 + 0.0) / variable2