For clarity, the progress bar is a visual indicator of that particular day in the Challenge. So for Pre Season Day 1 the progress bar will show at 50% (because there are 2 days in preseason, so day 1 is at the half way point). On Pre Season Day 2 the progress bar will show 100% complete.
The progress bars are not linked to the achievement buttons, they’re simply a ‘quick look’ at where that particular training day falls in the overall Challenge training.
Hope this clears up any confusion.