Please reply with the version of ANSYS you are using.
You didn't explain the meaning of the term: fact.Ampl.
So one cycle of fatigue loading will be (step 1 then step2) and that cycle will be repeated on the assembly until it fails.
You mention that you have a three part assembly and that the parts are made of steel and aluminum. Are the three parts held together with fasteners? Can you insert an image of this assembly in your reply?
What material data do you have for the steel and aluminum? Do you have Yield Strength and Ultimate Tensile Strength? Do you have S-N curves for each material? Do you have the Endurance Limit or Fatigue Limit strength values for each material?
When you apply 12.9 kN to the assembly, what is the maximum Equivalent Stress in each part? What is the maximum Max Principal Stress in each part?
Where is the maximum stress in each part? Can you insert an image of each part and show the location of the maximum stress?