Two older and separate disciplines in which letters are numbers. In Hebrew, the 22 letters carry fixed values (aleph 1 to yod 10, kaph 20 to tsadi 90, qoph 100 to tav 400, with the final forms sometimes counted higher); in Greek, the Ionic numerals give the same three-tier arrangement, which is what makes isopsephy possible. Both are exegetical tools for reading a sacred text, not systems for reading a person.
The Hebrew values are already catalogued in hebrew_letters.json, whose value field carries them for all 22 letters. This entry records that the system exists and points there rather than duplicating the table.
Gematria is a family of methods, not one: mispar hechrachi (the ordinary values), mispar katan (each value reduced to a digit), mispar gadol (finals counted as 500 to 900), and atbash, which substitutes letters by reversal rather than by value. Two words with the same sum are read as linked. That is a quite different operation from reducing a name to one digit.
Nothing in the library points at this entry yet.