Albert Barnes Commentary Exodus 38:21

"This is the sum of [the things for] the tabernacle, even the tabernacle of the testimony, as they were counted, according to the commandment of Moses, for the service of the Levites, by the hand of Ithamar, the son of Aaron the priest." — Exodus 38:21 (ASV)

This is the sum ... - “This is the reckoning of the tabernacle, the tabernacle of the Testimony as it was reckoned up according to the commandment of Moses, by the service of the Levites, by the hand of Ithamar,” etc. The weight of the metals was taken by the Levites, under the direction of Ithamar. The tabernacle is called the tabernacle of the testimony, or the depository of the testimony, that is, the tables of the law (Exodus 25:16).