Synchronizer calculation is off. Y means the synchronizer will (should) work, N means it won't. However, like I said, the calculations are off. For both of my previous captures, the synchronizer was predicted to not work but they did. It's a coin toss.
And ability is the most annoying part. In 5th gen, there's a chance (it seems like a small chance, but it could be 50%) that your Pokémon will have the opposite ability it should. For example, I just caught a shiny timid Buchuru with ability 0, but it had Tension (which is ability 1). I also have a ton more captures with wrong abilities. This is why we use emulators for shinies at the moment.
Also, if your Pokémon has the opposite ability, record everything including initial seed, what seed you advanced to, and the PID. If the synchronizer works when it shouldn't, the info would be nice too.