It appears there are no records of the highest number ever counted to. Because of that, it would be impossible to say what the highest number ever counted to is and any claims (see below) would be unverifiable. If you counted one integer per second every second for sixty years, you wouldn't make it to two billion, so let's say the record is less than that.

One experience:

I recently counted to "approximately" 258 quintillion googol.

Sincerely,

Daniel Robbins month 7/ day 20/2017