If you are unsure about something, just ask: “What do you mean by that?” Then check back to see if you really got what the other person meant. Allow the other to clarify. “So what I understand is …. Did I get that right?”
NOTE: There is a huge difference between “So what you are saying is….” and “So what I understand is …” The first puts the misunderstanding on the speaker; as if they didn’t say it clearly. In the latter, the listener is taking responsibility for the way they understand what is being said.