Questions about input params in Densification strategy

[Metro1998]

First of all, thank you very much for open-sourcing such an excellent rasterization library.
And I have some questions regarding the abstract section of "densification."

1. Regarding scales, I’m not sure why its shape is N rather than N x 3.
2. For colors, I’m unclear how the shape N x 25 x 3 is derived—does the 25 correspond to the spherical harmonics degree being 4?
3. Additionally, I’m not sure about the purpose of the two subsequent Features—what exactly are they used to store?