Sample Size Caliculation in QM lot

Hi Experts,

Iam Facing a issue with Sample size caliculation in inspection Lot.

the Sample size is 0 in the inspection lot still we maintained fixed Sample size to 1.

In the Inspection Plan:

I have checked in the inspection Characterstic and see the Sample Base quantity is 1.

We are maintaining Fixed Sampling type in Sampling Procedure.

The Inspection Lot is generated when doing GR to purchase order.

The quantity in the purchase order is 6

note: The same Sampling procedure works fine with other batch of different material.

please let me know why it is caliculating Sample size to 0. we need that to be 1.

Thanks in advance