1. Numbered lists are easy
2. Markdown keeps track of
the numbers for you
7. So this will be item 3.
This is a quote from the editing-help page. It's not completely intuitive what it means from that, but essentially, Markdown detects what you presumably input as a numbered list and always starts a 1, always progresses in numeric order. Since you can quote lists, it also occurs with plain blockquotes, but not in code formatting as demonstrated above. It is a convenience in some scenarios, but as you show, there are some points where it is a problem instead.
If you want to start at a different number, I recommend using parentheses rather than periods. Alternatively, if you are citing something in which the original source uses a period, then surround it with backticks to invoke code formatting on the number alone. It doesn't look all that fancy, but... unfortunately I don't know of an alternative method otherwise.
7. Is this in the docs? I began this with "7." (seven dot) but it came out as "1." instead. I'm guessing the software thinks I am starting a numbered list, and requires me to start with 1 and not 7.