That's what i thought, but what happens is a new round begins and let's say it's my turn. The store has 0 mules so i can't buy any. I do what i can in that turn, catch the wampus, go to pub, survey land. The next player then goes. The store still has 0 mules to sell. So his turn starts, he starts at town and then magically the store now increases it's mule count to 1, then 2, then 3. That player then buys all three and assigns them to his plots. Then the 3rd player goes and then fourth player, neither get any mules. Then the round ends.

How is it that when the round started and i went first, there were no mules to buy, but when it was player 2's turn, then the store now had 3 mules?

I thought the way buying mules works is that the store has a specific amount of them and if those run out, players (during the auction phase) sell ore to the store. In turn the store will then produce more mules that become available for sale.

The situation that's strange to me is that during the auction phase nobody sells ore to the store. Therefore there are no mules to sell. But after some AI player starts their turn, they somehow buy more mules, how is that happening? Like if they sell their ore "on the spot" and get mules in exchange?