If you meant the 75.81% on your profile: that is the Hit Accuracy, not Overall Accuracy.
The Hit Accuracy only takes scores that gave you pp into consideration, so it's aka pp Accuracy. The Overall Accuracy is not listed on your profile, it's only visible at the result screen, and it considers every songs.
Your old score is probably too low to give enough pp to affect your 80%. Once you beat your old score, it probably gave enough pp to show up in the Hit Accuracy.
What I don't understand is how the heck did you get an A with only 70% pass. Sorry your OP is just too hard to read so I had to take a guess.