Spawn at X Y Z living entity is glitching and spawning tons of mobs

Hello am currently working on a mod that adds the moobloom which can be bread and its baby will grow up but with my current procedure once the baby will be alive for 200 ticks (ill increase this number later) it should despawn and spawn an adult version, but it doesnt spawn just one adult, it spawns like 50 so kind strangers please help + the adults spawn at the block i spawned the baby on even tho the baby can move completely away from that block

https://www.mediafire.com/view/0fm93lm3bu4tt7j/ggggggg.png/file

https://www.mediafire.com/view/5u2lfnl3xj8udxt/image.png/file