The short answer is “There is no tolerance.”
According to NIST Handbook 133, the net quantity of content statement must be accurate, but reasonable variations are permitted. These variations are permitted only when caused by unavoidable deviations that occur in current good manufacturing and quantity control practices. A sample must “pass” two requirements: the Average Requirement and the Individual Package Requirement. A sample “fails” if either requirement is not met.
Click on the video link below for additional information about the Individual Package Requirement.
Packages that are underfilled by more than the Maximum Allowable Variation (MAV) specified for the package are considered unreasonable errors. Unreasonable shortages are not generally permitted, even when overages in other packages in the same lot, shipment, or delivery compensate for such shortages. These unreasonable minus errors, or errors that exceed the MAV, are based on the labeled quantity and are found in Tables in Appendix A of NIST Handbook 133, Checking the Net Content of Packaged Goods.
For more information, see Chapter 1 (General Information) in NIST Handbook 133, Checking the Net Contents of Packaged Goods.