question re: calories burnt using hrm or machine count

des618

So I've seen on here a lot about how the machines at the gym are not accurate for calories burnt and that you should really use a HRM because the machines and database here over estimate what you burn. I found it to be just the opposite at the gym today. I used the treadmill for 32 minutes with a combo of walking and running. The treadmill said 323 calories burnt. I wore my HRM which has a chest belt and it calculated 370 calories burnt. Is there something wonky about my HRM?