Why such a different loading score after 3 days?

I’m checking the speed of a site using developers.google.com

Three days ago it showed a good score of [color=#006400]95[/color] for desktops and a poor score of [color=#FF0000]28[/color] for cellphones.

Today, the same test gives a score of desktop [color=#FF0000]26[/color], cellphones: [color=#FF0000]1[/color] (!!)

When I load it on my cellphone, it seems like the avarage loading time.

Why do I get these deviant results? What am I missing here?