We had a similar conversation recently. It was looking at the entire charr population, not just the ones in Ascalon, but the conclusion is still applicable- the legion structure lets us make some pretty loose estimates, but there’s no official answer. I encourage you to read through it (it’s a pretty short thread) and, if you like, use one of those equations while only accounting for the tribunes in Ascalon.
R.I.P., Old Man of Auld Red Wharf. Gone but never forgotten.