perfmon counter interval question

Hi All

I am trying to capture the Perfmon data for below counters, and ihave specified the Sample interval as 15 seconds. but i am confused with below points

1. does the value it collects is the point in time i.e the value at the 15th second

2.else it is the Average value it collects of the defined interval of 15 seconds.

Perfmoncounters:

• \LogicalDisk(*)\Avg. Disk sec/Read
• \LogicalDisk(*)\Avg. Disk sec/Write
• Memory – Available Mbytes
• SQLServer:Buffer Manager – Buffer cache hit ratio
• Processor – % Processor Time