Minecraft wiki entry for Chunk_format, associated text: This TAG_List is always present, and contains 16 TAG_lists, each representing one of the "sections" of the chunk. Those inside lists may contain TAG_Shorts, each representing a packed coordinate relative to the section : The 4 most significant bits are always 0, then each group of 4 bits (or nibble) represents a section-relative coordinate, from 0 to 15. The order of sections in the list appear to be ordered from bottom to top, and the packing order of the coordinates is 0ZYX. When converting proto-chunks to full chunks, only coordinates that are stored in PostProcessing appear to receive a tick update, tick updates stored in block_ticks and fluid_ticks are ignored. [verify]