Retroactively Add Starting Mileage for Gear

Hello!

When I switched over to intervals at the beginning of this year, I’d added my shoes as gear with their starting mileage. Intervals had been adding to that starting mileage since when I tagged them by run. Somehow that starting figure got wiped recently, so I now only see the totals from the activities I’ve added the shoes to in Intervals. Is there a way to insert those starting values back in and then update with the tagged activities? Thanks!