Valve fixed a bug that affected the MMR during player calibration. This was one of the developers of Dota 2 reported on reddit.

For ease of understanding, we will call these roles traits, functions, or features of the hero. Or even simpler: “That-what-hero-can-do-based-on-his-characteristics.” Drawing an analogy with the CCI, a hero is a card that is played by a team and performs a certain function. Or, by analogy with football, the one who kicks the ball hardest and most accurately, the striker, the one who jumps the farthest and all, the goalkeeper.

Carry will bring victory to the team. Their potential depends on the items collected. At the beginning of the game, such heroes are usually weak at the initial stage of the game and therefore act under the protection of heroes who can fight much more successfully at the beginning. Having accumulated a critical mass, these heroes, when used correctly by the player, become the key to the victory of the team.