You can adjust the paper folding position used when performing saddle folding.
This mode can be set when the Booklet Finisher-G1 is attached. (See "Staple Finisher-G1/Booklet Finisher-G1/External 2/3 Hole Puncher-B2.")
1.
Press 
(Settings/Registration).
(Settings/Registration).2.
Press [Adjustment/Maintenance] → [Adjust Action] → [Adjust Fold Position].
3.
Select the paper size to change → adjust the folding position by pressing [
] or [
] → press [OK].
] or [] → press [OK].