Numbers rounded to one decimal place are shown as integers when the decimal would show a zero: what is happening and how do I fix it?

I have basic bar graph that can be filtered to different subsets (e.g. different US states). I need to show labels with two significant figures, which I do using a calculated field and setting the number format on the value field to 'Number (Standard)'. This works, except that values that should be X.0 are showing as X (one significant figure rather than two). Other tenths-place values appear fine. So 4134 is correctly showing as 4.1k, but 1950 is incorrectly showing as 2k. The 1950 should show as 2.0k.  

Why is this happening and how can I fix it? 

Simplified packaged workbook attached, as well as screenshot showing the issue (as occurs for 'Special-use areas' when only Arkansas is selected).