The 64圆4 for each wall is an exact representation of a 4-block square in game.They do not include a palette icon or corners (the palette icon is generated in editor). Unlike the roof textures, the size of the wall textures are 64圆4. You should note that in the 64圆4 portion, the outermost 16 pixels in the texture will not repeat unless they are at the end of the roof (they are the border edge).The top right 32x32 in each set are the corners of the roof for when your roof is not a perfect rectangle.This is an exact representation of what a 4-block square of your texture will look like in game. The bottom 64圆4 pixels in each set is the actual repeating (or "autotileing") texture for the roof.This will not affect how the tile will look on the map. The top left set of 32x32 pixels in each set is the icon for the texture that will show up in the tile palette.Roof: The first 96 pixel row is all separate roof textures, each with a size of 64x96 (8 roofs per row). There are 3 rows of roofs and 3 rows of walls (totaling 24 roofs and 24 walls). The A4 is a combination of both autotile "roof" textures, which work the same as the floor textures in A2, and autotile wall textures.
I recomend that you open a pre existing, fully functioning A4 tileset while reading this so that you can follow along more easily. Firstly, each part in a tileset must follow an exact pattern, so you may want to use a pre-existing A4 as a template.