The first 10 digits of an API are standardized (first 2 digits are state, next 3 are county, rest are unique). 12 and 14 digits are not standardized (change based upon data vender/company) but signify:
- 11/12th digit designate bore. So if a well is sidetracked or multi bore these digits change accordingly
- 13/14 digit designate completion number. So if a well has more than one completion (recompletion, etc) these numbers change.
Most of us only look at the 10 digits but the 12-14th are important for geo/engineering.