OCCSOC some rows have XX in the SOC codes

I am processing the occupation of persons using SOC codes, however there are some rows that have XX and I am not sure how to process those records. Please advise. Thanks

OCCSOC is a 6-digit alphanumeric string variable. This means its codes can include both numbers and letters. A crosswalk of OCCSOC codes for the 2000 Census and the ACS/PRCS from 2000-onward is available here. You can see in this crosswalk that there are a number of OCCSOC codes that include Xs or Ys. The crosswalk gives, for each OCCSOC code, by year, the occupation title. You can use this information to determine what the corresponding occupation is. For example, near the top of the table, you can see that the OCCSOC code 1110XX in the 2018-onward ACS and PRCS represents “Chief Executives and Legislators.” How to handle these string/alphabetic characters is up to each individual researcher; we provide OCC as a fully numeric classification.

Thanks, very insightful!