Bose and Lin introduced a class of systematic codes for detection of binary asymmetric errors. Later, in [4] this class was generalized and the Generalized Bose-Lin (GBL) codes were introduced. In this note, we describe a Generalized Bose-Lin codes of limited magnitude l. For these codes, the possible undetectable errors are characterized, the undetectable errors of minimum weight are determined and the number of undetectable errors of minimal weight is found.