The new Arbys' "four roast beef sandwiches for four dollars" promotion?
Seriously now, absent the actual clip and assuming you posted the entire phrase, this sounds to me like a (relatively poor phraseology) initial call-up where the pilot is stating the altitude currently at and the altitude assigned. "Aircraft XXX, four thousand for four thousand," although I suspect you may have missed the first part of that call-up that may have indicated that the first "four" was hundreds of feet, not thousands of feet.
In the US, IFR aircraft are supposed to include their current altitude and assigned altitude in the initial check-in on a new frequency.
"Aircraft xxx, two point four for four" is a commonly used check-in phrase (altitudes would vary, of course), which means "altitude two thousand four hundred climbing (to) four thousand (assigned)."
A better check-in would be "XXX approach, aircraft XXX, two thousand four hundred climbing four thousand."