How difficult is the transition to multi-cellular life?

[ProxCenBound]

I'm thinking that we could have around 300-500 Earth-like Garden Worlds (even these would only be approximately Earth-like, and most would not support unmodified humans because of biochemical incompatibility);
around 300 ocean worlds with marine fauna (including Europan type worlds and tidally-locked eyeball worlds)
around 300 Titan type worlds with Muuh-like methanogen fauna
around 300 Amunian type worlds with ammonia based biospheres
around 1000 jovian biospheres with macroscopic life, like Ruach
and 1 magnetobiota (the Menexenes). Total: 2400(ish) garden worlds of all kinds. If we keep the 256 figure the total goes down to around 2150 worlds.

Also 158 vitriolic worlds, 356 halogenic worlds, more than 60 seeded Earth-like worlds (in the Garden of Paradise and in the Cybiota realm) and 34 neutron star biospheres, which are relics of artificial ecopoeisis rather than natural abiogenesis. Some of these have seeded nearby systems through panspermia, so they are equal to natural worlds in many ways.

This sounds mostly good to me, although I would lean towards 500 Earth-ish garden worlds. Also, I concur that 1,000 jovian biospheres seems too high, why it would be the most common place for life to develop? Perhaps 50 or 100 would be better - seems like a difficult place for abiogenesis.