Seven Thunders Mystery - What did they say?

Revelation 10:2-4 He was holding a little scroll, which lay open in his hand. He planted his right foot on the sea and his left foot on the land, and he gave a loud shout like the roar of a lion. When he shouted, the voices of the seven thunders spoke. And when the seven thunders spoke, I was about to write; but I heard a voice from heaven say, "Seal up what the seven thunders have said and do
not write it down."