Kendrick continues the extended metaphor about balls and says he’s balls deep. When you’re balls deep your balls are still out while you’re in the pussy. That’s why he says balling out in the next line to tie into this line
Also, when your balls deep the pussy is about as full as it possibly can be. So metaphorically Kendrick is saying that he is filling up the music industry; giving it as much as it possibly can take to the point that it is overwhelming. Kendrick is overwhelming the game with his superior talent.
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