Category statistic

hi SafeGraph community,

i got a question about the category statistics. i filtered data by specifying the NAICS code to "81211”, and the result is shown below. if my understanding is correct, 812111,812112,812113 are subcategories under “81211”, and the sum of POIs for these 3 subcategories should be equal to the POIs for ‘81211’. but the table below showed differently: pois for “81211” is much larger than the sum of others.

Can anyone provide some insights or explanations for this problem? Thank you very much!