Think of it this way...
Six deck shoe. If all cards were played before shuffle, after the last card the count would be zero. Now if you stop at any point during that six deck shoe, the count will indicates two things. What has happened up to this point and what is likely to happen in the future. And they have to balance out. So if you stopped 3 decks into a six deck shoe and the count was significantly negative, that means that going forward, the remaining 3 decks would be played at a disadvantage, with more small cards coming out. Conversely, this means that the 3 decks already played with the high cards coming out were played at an advantage, it is just that you didn't know it until after the fact.
So a negative count at any time, only indicates a disadvantage, GOING FORWARD. The hands that were already played were played at an advantage.
So if at the shuffle point, the count is negative 30 of 33 times that means that IF you played another hand, which you can't, you would be playing at a disadvantage, but the previous hands were played at an advantage.
Again, what you have to worry about is the complete opposite scenario. Each time you get to the shuffle, the count is positive. That COULD indicate that small cards have been removed and you are playing at a disadvantage.