Yeah, lots of free space there ... but keep in mind, a data file will grow to it's size for a reason. Shrinking usually only results in the file growing back. Regardless, if you need to shrink, you need to shrink. I wouldn't shrink it all the way down ... usually good to leave some room in the tempdb. Actually you should match the amount of data files to the amount of CPU's for better performance.

Anyways, run this:

USE [tempdb]

GO

DBCC SHRINKFILE (N'tempdev' , 4096)

GO

Then re query your size. If nothing has changed, check the error log (sp_readerrorlog). See if there is anything about a wait or stall.