what affect spawner spawn rate?

[ThoriumCrysis]

What affects the spawn rate? Because when I was grinding the one block, my spider spawner didn't spawn many spiders. But when I approached it, a lot of them appeared. aanndd I accidentally placed a squid spawner 1-2 blocks away from the spider spawner. Is that disturbing and it seems like the squid isn't spawning...

 

[FaroukUN1]

What affects the spawn rate? Because when I was grinding the one block, my spider spawner didn't spawn many spiders. But when I approached it, a lot of them appeared. aanndd I accidentally placed a squid spawner 1-2 blocks away from the spider spawner. Is that disturbing and it seems like the squid isn't spawning...

its called a mob cap
basically if you already have alot of mobs nearby the spawner will spawn less mobs(to keep the server from lagging).
also nothing will spawn if it is not loaded by a player(such as you)