To keep adding to already edited picture, we see 7 different red circles/ellipses I added, from left (1) to right (7):
1 - it just happened out of hitting the stones in angles all kind of wrong or applying much pressure on the very heel at first not knowing; getting afraid; trying to keep the scratches thereoff lower still unsure do I want to go there/what's there. Checking my other side often. OR... distancing my pressure points way too much because these where my first strokes and I didn't know what to expect at all.
2 - a clear two finger falling back into more pressure yet getting quite shy right after again. In the right after, we see...
3- a shift of one of those two fingers in 2, for a couple strokes. Hard to determine, was it seeing that spot, or just the much more plainer #2, that got the OP so shy in the following segment? That following segment I did not circle is what makes me doubt of the otherwise so very obvious first "overgrind" I did NOT circle neither. In my sense, no real as much pressure/work at all ever happened there. If a getting scared thing it was applyting pressure close to tip of heel in an exploratory fashion and realizing angle was off/these stone things are acting weird with angle/what I see. SP320 is good at that.
4-Another clear two fingers, now somewhat distanced. Trying to get the bearing of this thing and close/distanced fingers or wrong judging of how the sratch pattern carries have proven real scary real fast so far.
5- I'd say, starting to understand pressure level has more effeciency. and understanding there is no going back for sure by now. Two fingers but with one now overriding the other? A common mistake/happenstance of unsure sharpening/thinning/polishing of such kind almost naturally occurs where a blade gets much narrower for someone not execting/foreseeing it as a more delicate area to thread on. More pressure also a common mistake of feeling the angle applied before not touching/feeling like it did an inch before.
6-7 bla bla bla....