OK, so you have a disk that Windows recognizes as being ~300GB (the difference is accounted for by the fact that the drive itself measures 1GB = 1,000,000,000 while Windows treats 1GB = 1024 x 1024 x 1024) and a partition that's also ~300GB.
You still haven't told me how much "Used" space the drive shows in the "Drive Properties" dialogue box (double-click "My Computer" to see all the drives, right-click on the drive in question and select "Properties"). Please tell me exactly what it says in that dialog box for both "Free" and "Used" space (ie, 127,012,321 bytes). Those two numbers should add up exactly to the "Capacity" shown just below them, and judging from what you saw in "Disk Manager" it looks like the capacity should show as about 300GB.
It's normal for every drive to have a Recycler folder. There will be a recycler folder even on a brand new drive that has never had any files put onto it (as long as the drive is formatted as NTFS as yours is). You don't normally need to look inside that folder directly - instead you normally click the "Recycle Bin" on your desktop to see if there are any files in it for any of your drives.