Mono recording uses 90/180 degree wiggles. In other words, left to right wiggles. Stereo uses 45/225 degree wiggles for one channel and 315/135 degree wiggles for the other channel. So if a mono record is played on a stereo cartridge, the same signal appears in both channels. If a stereo recording has a perfectly centered sound, it would be (almost) 90/180 degree wiggles. This is one of the reasons why exact cartridge alignment makes such a difference in sound quality.