Aih sayang, takut jugalah when you see the red bleeding especially when kantung baru nampak kosong kan. But okay, light spotting in early pregnancy memang common, some mums I know had it masa kantung baru terlihat, mostly brown or pink, and just a few drops je. The fact that yours lepas 6 jam, amount sikit je (macam yang you describe), and doc already gave you ubat and a referral letter, sounds like doc is taking care of you properly lah.
That said, since your doc dah bg surat refer and you're feeling worried, I think worth going to the hospital jugak, bukan rush emergency, but at least they can scan again and confirm baby's developing okay, esp since the kantung kosong thing needs monitoring. Better peace of mind, and they can guide you on the next steps. Light spotting can be okay early on, tapi with the empty sac situation, better get the specialist to check properly rather than guess at home. Take care of yourself ye!