John Gill Commentary Exodus 25:35

"and a knop under two branches of one piece with it, and a knop under two branches of one piece with it, and a knop under two branches of one piece with it, for the six branches going out of the candlestick." — Exodus 25:35 (ASV)

And there shall be a knop under two branches of the same
According to Jarchi, from the middle of the knop (which was like a pomegranate, or, as others, like an apple) two branches were drawn from the two sides of it, here and there; so they teach in the work of the tabernacle, the height of the candlestick was eighteen hands' breadth: this clause is repeated twice in this verse, signifying there should be a knop under each of the three branches on one side, and three on the other side: for it follows,

according to the six branches that proceed out of the candlestick ;
out of the trunk of it, as in (Exodus 25:32) .