Hi Carol ,
it is the most difficult one
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Are you sure it is mandatory . 
Any manual process may be controlled by a GMP , frequency of line checks is only to ensure that team is still focusing , it does not grantee consistency or that all the products are the same
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OK let us think about it .
1- Gross weight consistency : you can use a check weightier with a print out ,this will be a good verification for gross weight.
2- Number of amount as declared on pack: no grantee but we can say within accepted tolerance , but
A. Use a composite sample , take samples of your finished product from the same shift and calculate the average , if it is matching OK release it ( in my country sample size is 32 pack ), I'd like to review your local legislation .
B. It is more cost ( may be stupid , but with a good results ) make it on two steps : 1st prepare a pre-mix step then 2nd a filling step in the second step a verification that 1st step is OK , here it seems that each pack is samples and verified .
Or make it like the Mixing/filling team does not seal the pack , someone is a backup to count /assure then seal it for sale .
Finally it is about be in tolerances as below
https://www.fsai.ie/faqs/quid.html
How should the calculated QUID value be declared on the label?
The QUID declaration is an average quantity, obtained by complying with the recipe and good manufacturing practice, allowing for the producer’s normal manufacturing variations. The stated quantity should be rounded to the nearest whole number, or to the nearest 0.5 decimal place where the quantity declared in below 5%
hope this helps , good luck ,
Ehab