It might not be lying.
Frame data for aerial moves are always difficult, if you look at data for most games it will actually have either a range or not be displayed.
When you land on the ground, your animation cuts short so the actual advantage on block will change, at LOWEST height maybe it is +6, but if you get it blocked at the max height, you might recover fully in the air at +1.
It may be that you can't actually get the move blocked while being high enough for it to ever be +1 because there is no air blocking, but the move itself would still be +1 in a vacuum because if the animation was allowed to fully complete, that would be the advantage.
That said frame data in game is bork anyway, they should have a system for calculating frame advantage like Skullgirls does (not that it is perfect either, it works in 95% of situations instead of like 33% though) instead of manually inputting data. There are so many mistakes.