In general, you can enter a different series in the order field if you have an available series.
To add a new series, find the appropriate group in the First Free Number session, and add a new series and first free number (usually 1).
In Baan IV, go to the Maintain First Free Numbers Session (under Common, Tables, Maintain Logistics Tables, Maintenance 1). Groups are easily identified (e.g., Purchase Order, Sales Order, etc.).
In Baan V, go to the First Free Number Session (under Common Data, Tables, Logistics). There are number groups (e.g., 570 may be for Purchase Orders, 650 may be for Sales Orders, etc.).
In LN, go to the First Free Number Session (tcmcs0150m000 – it is in different places in the menu under different Feature Packs). There are number groups (e.g., 210 may be for Purchase Orders, 310 may be for Sales Orders, etc.).