Should be "At exactly" not "Exactly at" and without comma. Reported.
Options with "at exactly" are among the accepted translations.
I drank my first beer at four precisely. Or it has to be "precisely at four"?
By the way, what does this sentence have to do with science?)
From the life of a scientist, working 8 to 4.
As to my experience in Czechia everything has something to do with beer. And I am to admit that I love it!