If it were me, I'd just keep adding distilled water till the new tank arrives.
( what's that, 85 cents a gallon ? )

When you replace the tank, top it off with distilled water again, run it a few days then check the antifreeze level ( good to -20F or such )

but again, if it were me, Id replace the tank, do a complete flush and refill with 50/50
Zerex G-05 and distilled water.