Guidance required for submitting ERC: what Filename format will be accepted?

When submitting a new ERC, the EIP-validator is always complaining about the filename.

I have tried several formats as seen in other PRs, but nothing works out today:

Error: file name “erc-gesact-security-tokens” not in correct format
Error: file name “erc-x” not in correct format
Error: file name "eip-draft_security_tokens_gesact" not in correct format

(referring to Add ERC: Crypto Security Token Smart Contract Interface by itinance · Pull Request #85 · ethereum/ERCs · GitHub)

Which filename format will be accepted?