Top Vapor vapes are generic models made by Wenzhou Yixin in China. The same models are made for other companies and given different names. Wenzhou offers no warranty. Hopefully you got some kind of warranty from the reseller.

The temp on display should only be used for a reference point. Hopefully, it's accurate enough to serve that purpose. As far as showing the actual vaping temp, forget it. Find the vapor range by starting low and see where you start to get some vapor. Find the high end, where the vapor is harsh and your remains are very dark brown/black. Your preferred temp is in between these points, where your remains are light to medium brown.

You should load at least enough to cover the screen. You can load it half full if you like, but keep in mind that you need to stir it up once in a while to get it all exposed to the hot air stream. The more you load, the more you have to stir and you'll be vaping quite a bit of ABV (Already Been Vaped weed). This compromises the taste. Also big loads, that give you big hits, are somewhat wasteful. The bigger the hit you get, the more vapor you'll be exhaling, and that's a waste. You can't take in a big hit, hold it for 2-3 seconds, exhale and get all the effective compounds.

Don't use chunks. Grind it. Grind with your fingers if you have to, but then you lose a lot of good stuff on your fingers. A very few vapes are designed to use pieces instead of ground, but this isn't one.