How many celsius shuold be the heat gun setting?

I personally go halfway on the dial. I have no idea what that exact temp is since my gun just has +/-. The exact temp is really not important. It only needs to get hot enough to loosen the adhesive, which should be around 100F.

My method for doing tablets is pretty simple:

start at one corner and heat up the glass along both edges until its hot to the touch. Not warm, not scalding, just hot. Then I start prying up the glass from that corner. When it starts getting tough again, I heat up from that point to the next corner. I keep repeating until all the glass is up.

You will never find 2 techs who use the same temp settings on anything. We all have our own way of doing things and different tools. Heck...I still have no idea what temp setting I use for hot air rework. I also don't care.