So my vision is -2.25 in both of my eyes but I was wondering what this means in terms of 20/20?

It could really vary. Terms of 20/20 is very inaccurate. For instance, if your vision was 20/60, then you would see something at 20 feet that someone with perfect vision could see from 60 feet. Can you see how that would be very iffy? This is the reason that prescriptions are not written in these terms. Vision screening (20/20 charts) are simply just to get a rough estimate.