Why I don't get all results in my chart Axis despite having enough room in SSRS?

I'm having issues displaying all the user under my chart despite having enough room. Everything works well as long as I don't have 10 or more rows in my result query. Increasing the size of the chart and playing with the Axis properties did not work.

I'm using Visual Studio 2008 (Yeah, can't do much about it). Do you have maybe an idea what's going on? Maybe this is a limitation of the older Visual Studio?

Chart with issues:

Good chart:

You can force the axis to whatever internal you require. The default 'Auto' setting often gives undesirable results.

Right-Click the Axis you want to change and select 'properties' then then the 'Interval' to '1'