Verses 20-21 are identical with 25.34-35, except that the word lampstand is repeated at the end of 25.35. In verse 21, however, the Hebrew simply has going out of it. In verse 20 the verb were has been added in translation, since there is no verb at all in the Hebrew.
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 .