Good idea to confirm the level before doing anything but 500 is bit high which may cause cloudiness and/or scaling. The only practical way to reduce it is with a partial refill. Amount of refill will depend on your tap water CH so you may want to test that too.

Also, since 500 is not extremly high, you could operate with it for a while but I would lower your PH to at least 7.4 and alkalinity to 90-100 to help reduce the chance of scaling until you can refill. Without a heater or SWG, the only real risk for you is scale on the tile or a cloudy pool.