Sorry but not easy, in French I can but in English is very difficult for me as I’m not sure of the correct wording for “cog offset”, in French we say “deport de denture”.
This is usual way to match cogs on an automotive manual gearbox as distance between input and output axis is fixed but with couples of gears for the different ratios and it’s not possible for a same axis distance to have different ratios with normal machining. So there is a special machining to allow gear matching. This machining gives a little bit modified teeth shape, can be thicker (stronger cog) or thinner (more fragile) depending if positive or negative offset.
It’s also used to reinforce the smallest cogs which are more fragile and I think this is the reason of Florian choice for a planet of 14 teeth instead of 15 which should be the standard with sun gear 36 and ring gear 66. 14 teeth planets with offset are stronger than 15 teeth for the same (in fact almost) cog diameter.
Additionally, epicyclic train of 36/14/66 is compatible with 6 planets against 5 planets for an epicylic train of 36/14/64 and so planets receive less stress as they are 6 instead of 5 !
Great concept !