Golly, um. PR from 2015 was 3:24, or 204 minutes. 4% of 204 is 8:10 minutes.
I'll be overjoyed to hit 3:45 this year, or 225 minutes. 4% of 225 is 9:00 minutes.
I'll be disappointed to go over 4:00, or 240 minutes. 4% of 240 is 9:36 minutes.
Also, I doubt the shoes actually do that. Maybe if you were wearing wooden clogs before...