Yes, 45 degrees. 12:20 in the video I posted is a good angle with a bigger clock to compare. If I had to pick I’d say it was 4, but I’m not sure the requirement to reverse challenged calls…is it like the NFL where it’s supposed to be overwhelming evidence or whatever? If that’s the case I don’t think it was enough to overturn, and I presume deciding that was why it took so long.
I initially thought Rivera’s hand movement towards the end was an attempt to signify he broke 45, but I’m not sure, as @fishbane alluded to, it probably looks more like he was winding up to swipe but changed his mind.