"Wait, transition is used only 0% of the time? That can't be right.
This data is for a CSS shorthand (eg: background) which is normally expanded to the appropriate longhands by the browser's engine and placed into the CSS Object Model. In some instances this can not be done, such as when a site uses custom properties. This results in confusingly low numbers, but the data for the shorthand is actually in its appropriate longhand. Click the link below to see the data for all of the longhands that map to this shorthand."
My guess would be that the scale only goes up to 99.x% and any values of 100 are being shown as zero.
Edit: ... and I was wrong. @blatherard has explained it.