Google speedtest

I am updating a site and checked "Google Speedtest".
I noticed something very weird, so I tested with

  • The first time I checked, I got a mobile score of 44 and a "Computer" score of 74
  • The next time (two minutes later), got a score of 39 and 75
  • The next time it got a score of 39 and 77

Does this make any sense ? Is not not strange that mobile score goes down and "PC" goes up at the same time ?