Post counter can be negative on creating topics with small time interval

Preconditions
User1 has permissions to post answers in Topic1
User1 has 100 posts (for example)

Steps to reproduce
1. Go to Topic1 and sent 3 posts with small time interval (i use XSS Me add-on for Firefox)

Actual result
Post counter for User1 has value 102

Expected result
Post counter for User1 should be 103

Note
There is some log info for queries which lead me to incorrect work for post counter.
File can be opened via Fiddler. Maybe we had some problem with time intervals so tab "Statistics" in Fiddler would be interesting.

Also if i delete some post - post counter becomes negative (see screenshot in attachment)