Would not hurt to have someone lay in the trunk than close the lid to ensure the trunk lamp is going out when the lid is closed. If it does go out than you will need to remove the bulb while performing the following test.

I noticed your meter is relatively simple in design, cake walk! Disconnect the battery (-), place a test light between the post and the cable, if it stays brightly lit than you have a significant draw. Insert the red lead into the 10A socket on the lower right side of the meter than insert the black lead into the COM socket. With the test light still connected to the battery and cable, clip your Red lead to the Battery Post, clip the Black lead to the cable, remove the test light and read “Current Draw.”

Get back to us with your test value.