No, "Start change text" is correct. It is referring to the "Start" text field in the Smart Change Detection feature, where you enter some text from the page source to look for. This is the start of the range of the page to examine, and the End text is the end of that range. Simon will only look at the text between those two blocks to determine whether or not to consider a change found.

The error you received indicates that the Start text did not occur in the page source. Perhaps the page template was changed significantly, or the text you entered was too dynamic. Try making it more general.