It sounds ok. I feed about 600-700 in mid flower. My runoff is about 1200-1600 depending on whether I water enough for good runoff.
I don't start having salt buildup problems until it reaches 2500. That's when the soil ph is around 5.2-5.4. A little lower that that is when the plant shows nute lockout. As I see it going above 1600 I'll deliberately reduce nutes next feeding, and/or add 50% volume for more runoff (mini-flush).
It's good your watching your runoff ppm because the *trend* will be more informative than a single reading reacting to a plant problem. After you learn how much you can feed, how much runoff to strive for, etc., you don't need to monitor your runoff. But, when you don't know what works, it's helpful to catch over-feeding before it appears in the plant.
Your soil and nutes may be different. But, to me, 500 in, 1000 out doesn't sound bad. If goes up over time, you'll want to be prepared to flush, feed milder nutes, etc. I'd err toward waiting until I saw symptoms in the plant. At least then you'll know where that limit is with you and your plants.