Hi Shareef,
Can you please verify the split in inspector at Requisition.LineItems.Accountings.SplitAccountings level?
The reason might be because user might have entered more than 2 decimal digits which doesn't come out to be 100% at backend. In Ariba UI screen, system is showing error because by default system only shows upto 2 decimal places and also do the rounding of the decimals which may be summing up to 100%.
Thanks,
Amit