- Create a superflat world with the seed: 7606204815140416435
- First, execute these commands: /gamerule doMobSpawning false and /kill @e[type=!minecraft:player] (untill all entities are dead)
- Teleport to 102 5 223 using /tp @s 102 5 223
- Execute the command 'Spawner 1', afterwards execute command 'Spawner 2'
- Observe the two spawners, only 'Spawner 1' will spawn slimes
Video proof: http://usetapes.com/v/TQQ1qEYHiC