These statistical tables are fundamental tools for preparing a sampling plan for a random product inspection. They give you the number of samples to inspect, and the maximum numbers of defects that is allowed.
The first table gives you the code letter for sampling. In this example, if the batch to check contains 5,000 pcs, and if you choose level II (which is chosen by default for most inspections), the letter is L.
The second table (for normal severity) gives you the useful information. The letter L means 200 samples must be checked. If you select the limits as 2.5% for major defects and 4.0% for minor defects, you reject the batch if you find more than 10 major and/or more than 14 minor defects.