A Certificate ID should be incremental based on the prefix.
Example: SAFE-1, SAFE-2, SAFE-3, CS-1, CS-2, CS-3.
You have different prefixes for different types of securities.
options are OPT
shares have a prefix dependent on the share class
SAFEs are SAFE
Convertible notes are CN.
Why do prefixes matter on certificates?
These just help everyone keep tabs on them when the stock is issued, particularly when the same person receives stock across multiple transactions. Besides this, the specific prefix you use is not important.