E1 Where does the Next number for document type IN comes from?

Hi Everyone

I want to ask  Where does the Next number for document type IB, comes from when a cost update is made by running the R30835 Item cost frozen update?

Our customer is facing an issue, when they make frozen costs updates to manufactured items by running the R30835, the kardex F4111 shows a document number lets say 181537 IB and then when a new lot is created the kardex shows a very high document number example 1053965

What could be the reason for this and possible solution or logical explanation?

Regards