Ambiguities of mode 3 penalties

[nummacway]

This is about this section of the Rendering page.

1.

Background scrolling: At the very beginning of Mode 3, rendering is paused for SCX % 8 dots while the same number of pixels are discarded from the leftmost tile.

This should state that SCX % 8 is actually the penalty. Footnote 1 mentions that we are getting up to 2 more tiles than we need to, so one could think that these mitigate the effect, which they don't.
It is also surprising that SCX % 8 matters, when the Window's presence incurs a flat 6 dots penalty no matter the value of WX % 8 (well, not that surprising if you keep in mind that the Window's left tile is usually completely visible). BTW: Will the window stop affecting mode 0 if WX was big enough?

2.

If that tile has not been considered by a previous OBJ yet

This omits the fact that this is in respect to only the current line and that not the OBJ but the OBJ's Pixel matters. You can guess the first from the general concept of the PPU and the latter is suggested by the first sentence reading "Only the OBJ’s leftmost pixel matters here". But it would be less ambiguous if this was clearly stated. I suggest:

If - in this line - that tile has not been considered by a previous OBJ's Pixel yet

or

If - in this line - no previous (left) OBJ's Pixel has been in this tile yet

3.

The document states that mode 3 lasts for 172 to 289 pixels. The difference is 117 (so is 204-87). However, the sum of all mentioned penalties is 110 (OBJ) + 7 (SCX) + 6 (Window) = 123.

If you could confirm (or deny) this, I promise to draw the image requested in #503. I'll even draw two because I believe you'll need one with SCX=0 and one with like SCX=7. And I promise to do it nicely.