Technically a minus handicap is for players like Biden who are terrible where strokes are basically taken away from their score.
For example, let’s say I have a -18 handicap on a par 72 course I would logically expect to shoot a 90 actual score or a 72 after the -18 handicap is applied.
A positive or plus handicap works just the opposite, strokes are added to your scores, as you can imagine the only players with a positive or plus handicap low amateur or near professional golfers.
Remember the purpose of the handicap is to allow people with a wide range of golf skills to play against each in as fair of a way as possible.
What is a "mulligan"