When Speccy runs, the reported temperature always drops about 10 degrees, then stabilizes. I've seen this across a few laptops and many different temp ranges. I installed Speccy orignially because my laptop was getting very hot. The laptop is in my desk and no other ambient changes are taking place. So, why the drop in temp? See attached example.
I don't know exactly but taking a couple of guesses:
Could it be that you have been using the CPU intensively before launching Speccy which has made your CPU run hotter, but then stop using other programmes while you are watching speccy?
Could it be that what you are seeing is Speccy itself using the CPU?
When you run Speccy (or any other programme) it will initially use your CPU intensively and so the temperature goes up.
Once it has done it's starting it doesn't use the CPU as much and so the temprature drops again.
(10 degs. does seem a bit much for that though).
You could try looking at the CPU utilisation using the task manager and see if this corresponds to the temperature fall in Speccy.
When I launch Speccy the CPU utilisation briefly peaks at 100% and then falls off again to about 8%.
If I do a similar thing with other programmes that go to 100% on start, then Speccy shows a corresponding temperature rise then fall again, but only by 1 degree or so.
As I say those are just guesses, maybe someone else has more experience.