Fractional qty consumption of Raw material to create finished good

ERPNext Manufacturing
,
1

Error while submitting Subcontracting Receipt:
Total qty -1.0 of Serial and Batch Bundle 7d25a52f9bf688ee6dcd is not equal to Actual Qty -0.067 in the Subcontracting Receipt MAT-SCR-00019-3

my case:
Finished Item A → Serial No enabled
Raw Material B → Serial No enabled
BOM:
15 qty of A
1 qty of B
→ so per A = 0.0666667 qty of B
You sent 1 serial of B to subcontractor
Subcontractor returns 1 serial of A
ERPNext tries to:
Consume 0.0666667 qty of B
But serial numbers can only be consumed in whole numbers (1, 2, …)

How can i have fractional raw material consumption while creating subcontracting Receipt?

2

1 qty of B produces 15 qty of A right? Then subcontractor should return 15 qty of A not 1?