How do we rollup leadtime value if per unit value is less than a day

Hi

We are working in E9.1and using discrete manufacturing .We tried to run R30822A to roll up lead time value for all manufactured items. However it did not update manufacturing lead time based on routing hours defined. We have defined the BOM & Routing for fixed batch qty, which seems to be large. When we calculate per unit qty the value seems to be very less, say the calculated value in hrs. so we are not able to roll up lead time at product level. we have already setup QNTY field as 2 decimals, and even changing the field to 4 decimals will not have