Understanding Numeric Mention

2*f

This means the value (0) of the 2 multiplied variable f, which is essentially 2 x 0 = 0.

2f

This f is a literal representation of Java that indicates float (not related to the variable f).
This means that the number 2 is 2 of float instead of 2 of other types such as int (integer).

Processing float is inherited from Java, so you should refer to Java-related information for more information.