The meaning appears to be; “these are the yearly appointed times on which ye shall hold holy convocations and offer to Yahweh sacrifices, in addition to the Sabbath offerings Numbers 28:9-10 and to all your voluntary offerings.” Compare Numbers 29:39.
Related Commentaries of Leviticus 23:37
Leviticus 23:37-38
37 These are the feasts of the LORD, which ye shall proclaim to be holy convocations, to offer an offering made by fire unto the LORD, a burnt offering, and a meat offering, a sacrifice, and drink offerings, every thing upon his day:
38 Beside the sabbaths of the LORD, and beside your gifts, and beside all your vows, and beside all your freewill offerings, which ye give unto the LORD.