I guess the most useful way of describing the dot-decimal notation for IP(v4) addresses is that it consists of at least one and at most four numbers separated by dots, each of which represents on octet of the address (MSB on the left), save for the last number, which always represents all remaining octets. Each number is by default a decimal number but can also be an octal (prefix 0) or a hexadecimal number (prefix 0x). That should include all cases. Stuff like 10.05003 → 10.0.10.3.