Re: English help: "Run on line"？
Maybe it is asking if the item/product runs online, you know, like an app?
Otherwise, the only usage I've seen for this term has been noted: A run-on sentence (which is a sentence that contains multiple sentences that need to be broken up into independent sentences).
Or it is just extra space if you need to write in more. Best to clarify with client.
I don't understand what the form is trying to say, and I don't think it is weird or rude to write in, I don't understand the question or unclear.