A hull classification where the designated ship type precedes the number (e.g. CVN-68, DDG-67) is US Navy practice. The PLAN follows a hull classification system similar to the Royal Navy's in WW2, with only a number for each ship.
I'm not saying anyone is wrong here-- we can refer to the Type 002 as 'CV-18' and everyone will still understand what's being referred to. However, strictly speaking, it should be referred to as 'Ship Number 18' or only '18', assuming that 002 will receive pennant number 18.
For clarification, 'Type 002' refers to the class/design of ship, while '18' (or CV-18 if you're more comfortable with that) refers to a specific ship. There may be more than one Type 002, which may well end up with pennant number 19.