Purchase Order default BU

Hi, when you click on Create Order in the Purchasing module, there are a number of fields that are automatically filled in. Where does the information for these fields come from? We thought it might be related to Manage Users, but we haven’t been able to find the solution.

And I say solution because one user has been changed from one business unit to another, and now they have to change it manually. It’s a change that takes just a second, but we were wondering about that: why is one business unit assigned instead of another, and what does it depend on?