If you head to the hospy, they'll probably tell you to go home again for such a small amount. You're wise to stay calm, even though sometimes we can't help worrying! There's so many reasons for spotting - I wouldn't be worried over such a small amount unless you have cramping or pain along with it - all the best at the docs! Doc might refer you for an u/s for your peace of mind, or tell you to wait and see.