Comma is slang for money. In America, a comma is used to separate numbers consisting of 4 or more numbers. For instance, twelve hundred dollars is written as $1,200. This slang might not make too much sense to people from certain countries, such as those in Europe, whom often use a period in place of the comma and vice-versa.
This slang has been used by numerous rappers in Hip Hop songs such as in Future's "F*ck Up Some Commas" song in which he raps "Hundred thou, another hunnid thou - Three hundred thou to five hundred thousand - A million, let's have a money shower
Let's fuck up some commas."