hhmmm yes, seems a hierarchal pool was inadvertently/unintentionally created. i have no idea of your skill level so if you're not comfortable with any of the below... you should go to https://stablebit.com/Contact and open a ticket. in any event removing drives/pools from DrivePool in the DrivePool GUI should NEVER delete your files/data on the underlying physical drives, as any 'pooled drive' is just a virtual placeholder anyway.
if you haven't already, enable 'show hidden files and folders.' then (not knowing what your balancing/duplication settings are), under 'Manage Pool ^ > Balancing...' ensure 'Do not balance automatically' IS checked, and 'Allow balancing plug-ins to force etc. etc...' IS NOT checked for BOTH pools. SAVE. we don't want DP to try to run a balance pass while resolving this. maybe take a SS of the settings on DrivePool (Y:) before changing them.
so DrivePool (E:) is showing all data to be 'Other' and DrivePool (Y:) appears to be duplicated (x2). i say this based on the shade of blue; the 2nd SS is cut off before it shows a green 'x2' thingy (if it's even there), and drives Q & R are showing unconventional total space available numbers. the important thing here is that DP (E:) is showing all data as 'Other.'
under the DrivePool (E:) GUI it's just as simple as clicking the -Remove link for DP (Y:) and then Remove on the confirmation box. the 3 checkable options can be ignored because DrivePool (E:) has no actual 'pooled' data in the pool and those are mostly evacuation options for StableBit Scanner anyway. once that's done DrivePool (E:) should just poof disappear as Y: was the only 'disk' in it, and the GUI should automatically switch back to DrivePool (Y:).
at this point, i would STOP the StableBit DrivePool service using Run > services.msc (the DP GUI will disappear), then check the underlying drives in DrivePool (Y:) (drives P, Q, & R in File Explorer) for maybe an additional PoolPart.XXXXXXXX folder that is EMPTY and delete it (careful don't delete the full hidden PoolPart folders that contain data on the Y: pool). then restart the DP service and go to 'Manage Pool^ > Balancing...' and reset any changed settings back the way you had/like them. SAVE. if a remeasure doesn't start immediately do Manage Pool^ > Re-measure > Re-measure.
i run a pool of 6 spinners with no duplication. this is OK for me because i am OCD about having backups. i have many USB enclosures and have played around some with duplication and hierarchal pools with spare/old hdds and ssds in the past and your issue seems an easy quick fix. i can't remember whether DP will automatically delete old PoolPart folders from removed hierarchal pools or just make them 'unhidden.' perhaps @Shane or @Christopher (Drashna) will add more.
Cheers