Hi there!
You cannot use "event-offlineplayer" in a command, as this is not an event.
Events are triggers which are called when a certain thing happens in game, e.g "on block break", or "on any movement"
Commands, in your case, are not events, and therefore, "event-offlineplayer" cannot be used!
Instead, try using "add 200 to {balances::%player's uuid%}"
Hope this helps!