In a $15/$30 Limit game, the small blind is $10 and the big blind is $15.
For example, in a $2/$4 Limit game the small blind is $1 and the big blind is $2. In Limit games, the big blind is the same as the small bet, and the small blind is typically half the size of the big blind (but may be larger depending on the stakes). The player immediately clockwise from the small blind posts the 'big blind', which is typically twice the size of the small blind (blinds can vary depending on the stakes and betting structure being played).
Before the game begins, the player immediately clockwise from the button posts the 'small blind', the first forced bet. In Hold'em, a marker called ‘the button’ or ‘the dealer button’ indicates which player is the dealer for the current game.