The present disclosure proposes an operation method of a first device in a wireless communication system. The method may comprise the steps of: receiving, from a base station, information related to the maximum number of transmission resources which can be indicated by sidelink control information (SCI); determining a size of a field on the SCI, the field indicating the number of the transmission resources, on the basis of the information related to the maximum number of the transmission resources which can be indicated by the SCI; and transmitting, to a second device, the SCI including the field indicating the number of the transmission resources.