These handshape primes found in ASL (American Sign Language) are the smallest units of language (ASL). This set of handshape primes is called "handshape paramater".
A single ASL word/sign is made up of these five parameters: handshape, movement, location, palm orientation, and non-manual marker. Each parameter has a number of primes. E.g. there are over 45 handshape primes.
ASL handshape chart
The sign language handshape chart is organized into categories from "O" to "10" using the Handspeak categorization system invented by Jolanta Lapiak. Each handshape prime contains digits from ASLwrite. The digits are continually experimented and evolved in the ASLwrite community.
Those digits (regardless of the palm orientation in photographs only for the purpose of illustration) are based on the right-handed from the signer's perspective. For left-handed, simply flip the digits horizontally.