<p>I think within the context of the Marvel Cinematic Universe, the main world is 616 (which is known as the main world). However, in a wider context (including the comics etc.) The MCU is 199999 and the comics are 616 because that would make that the main world. If that makes sense. The MCU won't say they're 199999, because there are no other worlds that would be the comics. </p><p>
</p><p>In other words:</p><p>-Everything Marvel -> The main comics are 616 because that's the main world and MCU is 199999 (which doesn't account for the MCU's multiverse), as it is like any other alternative world.</p><p>-Everything MCU -> MCU is the equivalent of the main comics world (they're there own thing), so therefor they are given the 616 (= main world) title.</p>