Documentation Link

https://matplotlib.org/stable/gallery/lines_bars_and_markers/linestyles.html

Problem

The offset parameter is not an additional "start length", but how much of the dash pattern that will not be shown the first time. Although none of these are explicitly stated in the documentation, several (at least two, including me) have interpreted this as the latter.

Suggested improvement

Try to explain this better somewhere, ideally including a detailed example (now, all examples have a zero offset).