More precisely, from 1 to 4000.

In a garrison, the maximum number of monsters in one stack is 9999.
Neutral creatures indeed have a maximum of 4000. Thank you for the correction.

Sincerely, VDV_forever

Based on my gaming experience. If he places 1, diplomacy appears later, and the number of snipers increases.

I don't understand the meaning of your statement. :( Could you elaborate?

Also, I've never encountered less than seven.

The thing is that most often, a player manually places fewer than 5-7 units, i.e., on a map created by him, with the exact number of monsters specified (and with the indication that "the number does not increase").
You just haven't encountered such maps yet, but you have everything ahead of you!;

Sincerely, VDV_forever