Image forming system, control method thereof, and non-transitory computer-readable storage medium

A non-transitory computer-readable storage medium storing a program for use with an image forming system including:

• a storage unit configured to store a first recording medium and a second recording medium;
• an image forming unit configured to form images on the first and second recording mediums conveyed from the storage unit along a conveyance path;
• an insert unit, comprising a feeding tray on which an insert sheet is placed, configured to feed the insert sheet from the feeding tray and configured to insert the insert sheet between the first recording medium and the second recording medium conveyed from the image forming unit;
• an input unit configured to input information indicating a type of the first recording medium stored in the storage unit;
• and
• a detecting unit configured to detect a recording medium conveyed along the conveyance path,
• the program causing the image forming system to function to control a feeding timing of the insert sheet by the insert unit based on the type of the first recording medium indicated by the information inputted by the input unit,
• wherein the feeding timing of the insert sheet includes:
• a first timing at which feeding of the insert sheet by the insert unit is started after the first recording medium is detected by the detecting unit, and
• a second timing at which feeding of the insert sheet by the insert unit is started before the first recording medium is detected by the detecting unit.