The largest stackable Hethya incubator I could find holds 120 eggs, not 200. I don't know if I found yours or not but I'll comment on the 120 egg incubator.
I am not familiar with this make or model at all. That's not unusual, there are a lot of new incubators hitting the market these days since backyard chickens are becoming so popular.
Frankly, I would not buy his incubator. From the cost, it is cheaply made. The reviews I found say it is cheaply made, doesn't work very well, and soon breaks down. Instructions are poor and you do not get online support from the manufacturer. Since it is still in the box and you have time before you need it I'd return it if you can.
The instructions say to spray the eggs several times a day. I've seen that for waterfowl eggs but not for chickens, quail, or such. That makes me wonder how well the humidity works or how well they know what they are doing.
Brinsea, a well-respected but relatively expensive incubator manufacturer, specifically recommends to not spray the eggs. Any effect is temporary and you can spread bacteria if the sprayer or water are not sterile. Something out of the ordinary like that raises a red flag to me. I do not and would not spray the eggs.
I don't see how you control the humidity. Maybe there is some way you can adjust that through the controls. Some incubators can do that electronically. You only have one large water tank. One way of controlling humidity is through the surface area. If you have different tanks you can have water in some and have some dry. You don't have that ability.
It is totally clear which makes me wonder how good the insulation is. I'd use the foam box it is meant to set in.
To calibrate a thermometer I use one that is already calibrated (typically a medical thermometer) and directly compare them. Medical thermometers typically read very accurately in incubation temperature range. So assure that the medical thermometer is calibrated.
I don't have a specific recommendation of which thermometers to buy. Get one that reads to the tenth of a degree which means a digital. Some individual thermometers can be adjusted, some cannot. When you compare that to the medical thermometer and you get a difference either adjust it or see how much you have to add or subtract to get to the correct reading.
Sorry to be such a downer but I really do not like that incubator.