This is what makes 64x64 special. The bottom half determines "extra quality."
With the release of Minecraft Java Edition 1.8 and all versions of Bedrock (including Windows 10, mobile, and consoles), Mojang introduced the 64x64 dual-layer skin format . This doubled the vertical resolution. Now, the top 32 rows contain the base layer, and the bottom 32 rows contain the overlay (second layer) for every body part. skin minecraft 64x64 png extra quality