"cntr_value" returned by dm_os_performance_counters

We have a 3rd party tool that constantly complain about Sql Page reads/sec as being "critical". When I ran

select object_name, counter_name, cntr_value
from sys.dm_os_performance_counters
where counter_name = 'Page reads/sec'

I get these results:

12:50pm   487560303

12:51pm   487560430

12:52pm   487561738  

12:53pm   487561939

From what I understand cntr_value is cumulative. Subtracting the value at 12:50pm from the value at 12:51pm gives

127 but how is to be interpreted?  Do I divide it again  by 60 (seconds per minutes) to get an average of about 2.5 page reads/sec?   (And who is to say that that number, if correct, is too high or too low?)