Verse 30 is identical with 26.25 in every way except for the last phrase. Under every frame two bases is literally “two bases two bases under one frame” (repeating “two bases”), while in 26.25 it is literally “two bases under one frame and two bases under one frame.” Revised Standard Version shows this difference by shortening the phrase. Good News Translation translates the same in both places, “two under each frame.” There is no difference in meaning.

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .