Edit: Oops, I'm late to the party ;)
First, don't use +/- Par when talking about average, rather use gross scores (nine hole scores are doubled).
I'll replace "under Par" by 70 or 71, and "+1" by 73.
You are a Legend with an average of 70.42. The last 200 scores shown in your score history are all Legend scores, regular courses with a few Par3s and a few more Par5s in between. These Par3 and Par5 scores do not count towards the average.
Let's assume that you played 200 counting rounds as a Legend, meaning that your average ain't "saturated" (which comes with 500 Legend scores). Regardless of the actual number, your are below 500 because your average still rises on higher scores.
Thus, a 70 score may drop your average by (70 - 70.42) / 201, which is about -0.002, invisible due to the display with two decimals. Five of these scores would just be visible as -0.01.
A 73 score may cause (73-70.42)/201 = +0.013 - clearly visible
The extreme scores of the last week are a 32 on CCC and a 39 on Pebble.
The former may have resulted in (2x32 - 70.42) / 201 = -0.03 average change,
the latter may have caused (2x39 - 70.42) / 201 = 0.03 average change.
I call this "The miracle of the big numbers".
A few tips:
- Compare your scores to your average, not to Par.
- Be patient as the growing denominator will cause the steps to become smaller.
- Be double patient as you need 500 scores minimum to advance.
- Don't care too much of your average now, as - I'm afraid - most of these scores will fall out of the count when you approach 60.000 - the threshold to Tour Legend. This is particularily true for those scores raising your average now. On the long run, they are irrelevant.
Feel free to ask if you are out of practice in math ;)