I woke with a BG over 600 mg/dl this morning due to my pump becoming disconnected while I slept. My meter read “HI” and the manual says it can take readings up to 599 mg/dl. I typically run an A1C around 7.0-7.2. Most of my BGs stay below 250 (post meal) and often are under 130 (between meals). My guess is not much, but out of curiousity how much of a hit on my A1c would one episode of super high BG take? I have no idea how many hours my BG was high overnight. I last checked it around 8pm before I went to sleep and it was within normal range for 3 hr post meal.
One high blood sugar isn’t going to wreck your A1c, but I’m so glad you were able to get it back under control. Did you test for ketones? Jeez! You poor thing. Any kind of pump issue is so frustrating.
But no, your 7.0 shouldn’t suffer from that incident. Our A1c’s are most affected by sustained numbers and by high post-meal numbers. If you’re hoping to bring your A1c into tighter control, aim to have those 1-hour post-meal numbers no higher than 140 mg/dL and to be back at your pre-meal target by the 3-hour mark. I take a really fast-acting insulin (Apidra), but I still take it 20 minutes before I start eating to match my peak and the conversion of my food to glucose so that I don’t spike post-meal (a tip I learned here on TuD).
Probably won’t have much effect at all 
The last time I had a “HI” on the meter, I still managed to pull in a 6.3 a1c about a month later.