Can't generate Picklist in SAP Business One

Hi Experts,

My UoM setting:

• Inventory: Ctn
• Purchasing Ctn
• Sales: sqft or Ctn
• 1 ctn = 31 sqft

If the quantity in Sales is 31 sqft, SAP can't generate picklist after batch allocate.

If the quantity in Sales is 1 Ctn, SAP works well, but our customer needs sqft in SO.

Please advise me what should I do, thanks!