SolheartStud

SD assumes that the attack hits on the first possible active frame, but it is possible to hit with a later active frame. This is called hitting meaty. The usually occurs on wakeup where an opponent techs into an attack. In the case of Ragna's 5B it has 8 active frames and an SD of -7. This is only true if you hit with the first of the 8 frames. If you were to hit with the 2nd, you would inflict the same guard stun, but the move would be one frame closer to completion. This effectively makes the move -6. There are other factors that affect guard stun as well. Barrier adds one frame of guard stun, and IBing reduces it by 5 on the ground and 10 in the air.