Can your computers performance score change?

I built my gaming computer a month ago and I checked my score out've the five groups and they were. 7.9/7.9/7.9/7.9/7.8 now i checked randomly and they're 7.8/7.8/5.6/2.0/7.9 why did this change randomly it says the 3D gaming performance is only 2.0 but it was just 7.9 and i can still play bf4 on ultra.. i don't get what happened