Current draw is how much current a module takes from each power rail, measured in milliamps (mA). Manufacturers list it per rail, for example 40 mA on +12 V and 30 mA on -12 V.
Add up the draw of every module in a case and compare it to the supply’s rating for each rail. A common guideline is to stay below about 80 percent of the rating, which leaves room for peaks and future modules.