ok

I upgraded the shop to the latest version from 1.2.4

Customer placed order but had problems so I logged in as himand finished it. It created a new order as order number 0.

I used the 'change order number feature' and re numbered 0 to 2500. Then I created a test order to test it. the test order is order number 0 again

Where does it get the next order number from?

TIA