30 So there were eight frames and sixteen silver bases—two under each frame.

Read Exodus 36:30 Using Other Translations

And there were eight boards; and their sockets were sixteen sockets of silver, under every board two sockets.
There were eight frames with their bases of silver: sixteen bases, under every frame two bases.
So there were eight frames at the rear of the Tabernacle, set in sixteen silver bases—two bases under each frame.