On Monday and Tuesday, Numbers Plus Four went free under the KDP Select program. On Wednesday and Thursday, With Five You Get Fortune Cookies went free as well.
Compared with previous times when I made Numbers Plus Four free, I had similar results. The first time that the book was free in January, Numbers Plus Four averaged over 40 downloads per day. The highest ranking for the book on the free listing was #1,800 overall and #47 within the Short Stories category. This time, there were about 30 downloads per day. The overall ranking got into the 2000's, and the ranking within Short Stories peaked in the 40's.
With Five You Get Fortune Cookies did a little better. It had 34 downloads per day. While it's overall ranking among free Kindle books barely surpassed 2000 at one point when I looked, it was ranked as high as #9 under the Anthologies category! (see image below)
What does all this tell me? Other than that there appears to be fewer books under the Anthologies category than the Short Stories category, I'm not sure. I didn't see much difference between this week's results and the first time that Numbers Plus Four was free. The proof will come in the next few days. The first time around, I didn't get any additional sales as a result of the promotion. If having my books available for free this week results in just one sale, it will have been more successful than the last time.