clear_one_container.md

# Copy the last stone slot to a temp array
data modify storage temp Items[] set from block ~ ~ ~ Items[{id:"minecraft:stone"}]
# get the count in a scoreboard and remove one
execute store result storage temp Items[0].Count byte 1 run data get storage temp Items[0].Count 0.99
# Copy the last slot to the output items
data modify block ~ ~ ~ Items append from storage temp Items[0]