I followed Parallels' suggestion to reclaim 45GB of disk space and ended up with a corrupted Parallels Data File that cost me upwards of GBP 350 to have fixed. If I felt I had a chance of recouping that from Parallels, I would. In the meantime, I urge company to withdraw that faulty reclaim disk space function - and users should avoid it at all costs. (Latest MBP running Mojave and Parallels 15)