Paranoid

My son only drank 5-6 minutes on one breast and went back to sleep. I'm afraid he's not getting enough. I changed his diaper and put him back but he nursed for maybe a minute before he unlatched again. He's 6w. On the opposite breast I collected 1oz on a Haakka silicone pump. Do you think he only got an ounce from the breast or more since he's sucking it out?