After staring at this problem for a minute, I moved on. Turns out, this should be white to move. This particular theme occurs multiple times throughout the book and is pretty easy to spot once you know whose move it is. Overall, the quality of this book is excellent. Only 1 unusable problem, 1 problem with a better solution and 1 wrong diagram. I'd say that's pretty good considering some of the other chess books out there.
I sorted the problems the same way Rabbit did in his Bain Experiment. The only difference was my newer version of the text corrected the issue with problem 95, so I only had to discard 26. In theory, set F should be the hardest, and my gut says this is true. I also made a separate category for solution times over than 30 seconds and problems I gave up on after a minute, whereas Rabbit considered anything over 30 seconds as wrong.
Here's the histogram with the stats for my 1st pass through each set:
Two quick notes: I hand-timed set A. This resulted in an increased speed over relying on Anki for timing. Also, I did set F extremely tired. I should've saved it for the next morning, but I wanted to keep to my schedule. Even so, my results for 0-5 seconds was better than any other set, and my overall 0-10 seconds was second only to set E. Overall, it looks like a pretty steady improvement for each set, especially the under 5 and 10-15 categories.
The percentage of problems I completed under 15 seconds also increased, although not steadily. Heisman recommends being able to do 85% in under 15 seconds. Here's the percentage of problems I did in under 15 seconds in pass 1.
Set B: 29.23%
Set C: 46.15%
Set D: 33.85%
Set E: 58.46%
Set F: 40%
And finally, here's the percentage of problems I am currently doing under 15 seconds at each set's most recent pass:
Set A (5 passes): 81.25%
Set B (5 passes): 78.46%
Set C (5 passes): 89.23%
Set D (4 passes): 73.85%
Set E (3 passes): 83.08%
Set F (2 passes): 81.54%
I think I'm going to stop all sets at 6 passes which ends up being 52 days of study per set, and 75 days total from start to finish. I guess a good time to start revision #2 would be 52 days after I finish my last pass?
One final note: My stats indicate that I am holding steady or improving, even after my 5th pass which is a 13 day interval. Set A & B pass 6 is on the 12/22 and 12/27. It should be interesting if this is still true after a 25 day interval.
Up next is Woolum's The Chess Tactics Workbook. I am scheduled to start that 12/25.