I looked up the manual for the Oslo and it's the same as the castine. Optimal is 400-600. Any part of the stove glows red is bad and never open the ash door during a fire (even though I do for short bursts to get things going occasionally) otherwise you run the risk of cracking the stove.
I think a number of Oslo owners have done this when first starting out . . . and they either read more here and see pics of damaged stoves and immediately change their wayward ways and eventually discover that leaving the side door ajar may take a bit longer, but works almost as well (especially when paired with nice, seasoned wood and a Super Cedar) . . . or they disregard the advice or never stumble on to Hearth.com to learn better and eventually their stove is damaged and they're mad at Jotul for their "cheaply made" stoves.
I'm bugging of course, not familiar with the stoves mentioned.
, measured at the top corner on a Jotul 500, is too high = too much air, needs to be shut down.