I JUST installed one of those. They were sold by a member on here a number of years ago and they didn't come with any instructions. I remember posting the same question so an old search might turn up the answer but those instructions someone posted appear to be what I was told.

Worth noting is that the timing marks are not "etched" they're printed with some cheapo ink. If you wipe the damper with thinners they'll disappear! Since the thing is also bare metal and prone to rusting, I clearcoated mine - which smeared the timing marks but they're still good enough.