Fix runtime counter reporting

Hello, 
I've made small fix for runtime counter metrics.
Right now we report absolute values of this counters, but this counters are always incremented so we should report diff instead.

Otherwise we will get graphics like below:
![screen shot 2014-07-27 at 18 31 13](https://cloud.githubusercontent.com/assets/889406/3713794/d41a388c-1583-11e4-8c1f-ed483a327531.png)