How do I make a datapack track number of advancements made as a variable??

I'm trying to make a datapack where the worldborder expands by 1 for every advancement made but minecraft doesn't have a scoreboard or variable tracking that (I think) so I need to make a scoreboard where everytime an advancement is made it increases by 1 so that when wb.count is larger than wb.exp it expands. I looked at other people making worldborder expands when ___ but they all seem to use stuff with set scores like exp level which ofc is just a number and mob kills which is tracked in statistics so they use that.