According to Robert's Rules of Poker (
link), the floor's ruling here would be incorrect, although it is not 100% clear. I think the relevant rule would be this from the No-Limit section:
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4. “Completing the bet” is a limit poker wager type only, not allowed at big-bet poker. For example, if a player bets $100 and the next player goes all-in for $140, a player wishing to raise must make the total bet at least $240 (unless going all-in).
[/ QUOTE ]
The floor ruling looks like they are actually requiring you to 'complete the bet' coming from the BB here. Your actual options should be: fold, call 500, or raise to 4500 (or more) total.
However, there are no "official" rules of poker, and the final authority is always the house rules in place wherever you are playing. It would be interesting to see if the poker room you were playing at had published rules, and if so, does the floor ruling agree with what is in their rules.