PM Order Operations Default Unit of Measurement

Halo Experts,

We have a problem in UOM for PM/CS order operations. We have defined HR as default value of UOM for operations in IMG.

Business wants to change at the order level to H as UOM and it is manually keyed in and saved. But when we check with the F4 option for Unit of Measure " H" doesnt appear where as HR appears.

Any restrictions in displaying all the unit of measures. Can anybody clarify why "H" is not appearing on F4 option in the work order operation line items.

Regards,

Selva