MacBook Pro indicates in the storage management window 108.2GB available of 250.79Gb. Get Info of the Macintosh HD shows Capacity 250.79, Available 108.62GB (68.17Gb Purgable), Used 205.59Gb. Which is correct???? Operating on 10.15.2

Neither is probably right, but what is reported by Get Info or Disk Utility will be the most reliable. Trust the Get Info data.

Get Correct Storage Information

Do not use the information from the Storage section of the About This Mac dialog. Ignore the Storage information as it is typically wrong. To find out the correct information for any disk: Select a Desktop disk icon. Press Command-I to open the Get Info window and look at the topmost panel displayed. You will find the disk information displayed for Capacity, Available, and Used. If you have more than one disk/partition then repeat for each one on your Desktop.

The categories found in the Storage section of About This Mac is simply an arbitrary way of displaying files on your drive. There are no such categories actually on the drive.