Cannot save work item with total Time Tracking more than 999 hours in WebUI using Russian language

Using RTC 4.0, and the Formal Project Management, I found that if setting my Web browser's language to Russian,
and adding Time Sheet entries with a total that exceeds 999, I can not save my work item.

The steps I use:
1 - create a FPM PA
2 - create a task
3 - add time sheet entries until total reaches 990
4 - save
5 - change browser language to Russian
6 - add a time sheet entry to the total exceeds 999
7 - save
--> an error message is raised (Time spent value is not valid and work item is not saved) and work item is not saved

Note that switching the browser to English solves the issue.

If this a bug?