Sales always puff up for a few hours (2 to 12 hrs IME) after you upload a new listing.

I ended one and then reuploaded it a few MINUTES later, with a couple of minor changes in the description.

Then BANG, a slow few days was suddenly a bunch of sales in the next few hours.

It's always existing sales that puff up, and the length of increase seems to relate to how expensive the new listing is.

A higher priced new listing gets you more hours than a cheap listing.

Although I have had almost immediate sales of a new listing on the odd occasion.