all blocks can be read:

• andesite
• coarse dirt
• diorite
• dirt
• end stone
• granite
• netherrack
• sand
• red sand
• soul sand
• soul soil
• stone
• clay
• cobblestone
• gravel

blocks are compressed in a regular crafting table when decomposing 9 blocks of one of the listed blocks. 

examples:

an indicator of how much space is saved thanks to the mod: 

before:

after:

before:

after:

and the more blocks you need to compress, the more space will remain. for example , if you take 59049 blocks, then they can be compressed to 1 block