Bigtractor and KiotiJohn have the 540 PTO speed with the triangle. Check your owner's manual. It should tell you the same.
As stated before by many of the members, don't lug the engine. That's worse than running it at a faster rpm. My CK30HST is new with 9 hours now. I run it around 1500-2000 if I'm not doing any work with it, just driving from one place to another in middle range. If working it, I'm at 2400-2500. If you want to keep the rpm's down and keep from lugging the engine, use low range on the HST. Mine had one hour on it when delivered and the next day, we had about a 15 inch wet snow fall. It was out moving snow running it at 2400-2500. What a great job it did.
Enjoy the new tractor and don't forget the 50 hour service.