sparklines didn't work well on windows 7

I didn't try the examples on other OS but win 7
it turns out like this:
all the sparklines in the examples do the same display like the picture
Only me meet this problem?

The issue names no source file or test; start by running the sparkline examples on Windows 7 and comparing their output with the attached screenshot. Trace the entry point used by those examples to determine whether the display differs only on Windows 7, then verify the examples render correctly or document the confirmed limitation.

Written by the indexing model from the issue text.