Is this a typo?
The better measure is lifetime ROR, not ROR at a certain time. This is because ROR increases until you reach your lifetime ROR, and then decreases. If your ROR reaches its peak at n hands, you will have the same ROR whether you play n hands or 100*n hands. The number of hands only matters if you're playing fewer than n hands.
At 480 hours and 100 hands/hr (48,000 hands), you'll probably be pretty close to n (which is approximately the number of hands it takes you to double your bankroll, in your case, 300/0.006, or 50,000 hands).
Edit: beaten like a dusty rug