When the lead is member of an imported list, this lead becomes a member of the program where the list was uploaded

Hi Karina - this will only be the case IF you select that program name as the "Acquisition Program" in step 3 of the import process (and if they already have AP defined - within another program - you should not change this value).  Simply adding someone to a static list within a program will not make them members of that program.

Check out the bottom portion of this thread where we have a productive discussion around this exact topic:

Sample Questions for MCE Exam: Program Fundamentals