Hello everyone. About teeth. At 6 months old, the lower one came out, and…

Hello everyone. About teeth. At 6 months old, the lower one came out, and immediately the second lower one. At present, 8 months old, the gums swollen upper and it's clear that soon there will be teeth. Now I accidentally saw that the tooth is being cut, but not a single one, but a double... Aren't they coming out in order as everywhere written? Is this normal at all? ?Has anyone had this happen?