That partition is to save files which you don't want to be deleted if for some reason you have problems with Deepin or if you want to delete Deepin someday and replace it (maybe with an Deepin clean install) without touching these files. And, if you have another disk with Windows, that partition will be compatible with that system (as it is NTFS). If you don't need that partition, simply delete it with Gparted and add the free space to Deepin's one.
As personal recommendation, is always nicier to have important files in a separated partition from system, an even nicier to have them in another disk.