The multipliers increase your boards activity so that you can get more reward tokens.
The multiplier in each board is equal to the product of two multipliers:
The multiplier for holding coins of the specific board;
The multiplier for boosts applied to all boards.
Multiplier for coins
The more board coins you have, the greater your multiplier in this board.
The multiplier for board coins is considered by the formula:
Coinmultiplier = 1 + log (1 + board_coins),
where log is a logarithm with a base 2, a board_coins – the number of coins of this board on your wallet.
Thus, one board coin increases your activity in this board by 2 times, three coins – 3 times, seven coins – 4 times, and 50 coins will give you a 6.67 multiplier.
Multiplier for boosts
You can also increase your multiplier by completing small tasks and getting boosts that you can find on your profile page. Boosts are active while you meet their criteria, and apply to all the boards in which you participate.