Page 58 of A4 Mkii manual
“If both CLOCK RECEIVE and TRANSPORT RECEIVE are activated, the Octatrack MKII will wait for MIDI clock after receiving start or continue messages for 16 seconds before considering external sync lost. This, for example, allows for preroll in sequencers not starting clock until preroll is completed. If only TRANSPORT RECEIVE is enabled the machine will start as soon as possible after receiving start or continue.”