Set 7.5V on both channels, (On the measured CH1 and CH2 values Vpp, Vmax Vmin Vavg) connect DC voltage, press autoset (OLD version). Check the AVG value and write it here. Open the channel menu, highlight AC and then back to DC (don't leave the channel menu). Exit the channel menu, and check the AVG value again. Make video.
But it does not meet the conditions, written above.