Off Shed Descent after t/o

Hello!Today, i made two flights. The first was okay, nothing problem. At the arrival airport, i made the aircaft ready for the next flight. I set the the FLT ALT, and the LAND ALT. After takeoff, while i climbing, the OFF SHED DESCENT light turned on, and it illuminated until i reached my cruising altitude minus 1000 feet.What was the problem?Thank youDavid