[misc-] fix minor typos, and add-rows prompt

[midichef]

Three minor commits:

1. The first commit fixes a few self-explanatory typos.

2. The add-rows prompt (add rows: 1) is a bit vague. The new wording makes it just a bit clearer that what the user is inputing is a count of rows. Otherwise, they may think they're being prompted for a row index. Or they just may not understand what is being asked.