Hello fellow Stan users!

Very basic question here from a new user of Stan. I’m attempting to implement my first multilevel model, and I’ve been referencing some code that appears in the Stan manual (p151 and screenshot below). As part of the cholesky factorization optimization, the ‘group coeffs’ matrix is declared as matrix[L,K] gamma, where L = # of group predictors and K = # of individual predictors. Could someone explain why its dimensions are [L,K]?