Spotlight uses cpu_time from sys.dm_exec_sessions. That is a counter containing the number of milliseconds of CPU time the session has used since the session was started. Spotlight on SQL Server calculates a rate for that value using two successive collections and the time between the collections.
Spotlight could have expressed it as a % of CPU but chose to leave it in ms/s.
If you right click in the Sessions grid, a pop up menu appears. If you select the What's This? option, a help bubble pops up with an explanation for all the grid columns.
For this column it states the following:
CPU ms/s: The CPU time (in milliseconds) the session used per second. Use this column to observe sessions with high recent CPU usage.
So, if you sort descending on this column, what this means is that the highest cpu usage session will be at the top. The value in this column will be the number of milliseconds of a second that the cpu used. You can also select the row and then in the below tabs you can see the SQL and Plan Query (if applicable).
