Let T := T (A, D) be a disk-like self-affine tile generated by an integral expanding matrix A and a consecutive collinear digit set D, and let f (x) = x 2 + px + q be the characteristic polynomial of A. In the paper, we identify the boundary ∂T with a sofic system by constructing a neighbor graph and derive equivalent conditions for the pair (A, D) to be a number system. Moreover, by using the graph-directed construction and a device of pseudo-norm ω, we find the generalized Hausdorff dimension dim ω H (∂T ) = 2 log ρ(M )/ log |q| where ρ(M ) is the spectral radius of certain contact matrix M . Especially, when A is a similarity, we obtain the standard Hausdorff dimension dim H (∂T ) = 2 log ρ/ log |q| where ρ is the largest positive zero of the cubic polynomial x 3 −(|p|−1)x 2 −(|q|−|p|)x−|q|, which is simpler than the known result.