Rashi on Exodus 30:23/רש"י על שמות ל׳:כ״ג

1בשמים ראש PRINCIPAL SPICES — i. e. excellent ones.

2וקנמן בשם AND OF CINNAMON SPICE — Because cinnamon is the bark of a tree there is some of good quality, having fragrance and a pleasant taste and there is some which is merely like wood; Scripture therefore felt itself compelled to state, “Cinnamon בשם — with sweet scent”: of the good species.

3מחציתו חמשים ומאתים [AND OF CINNAMON SPICE] HALF SO MUCH, EVEN TWO HUNDRED AND FIFTY [SHEKELS] — The half of what is to be brought shall be 250 shekels; consequently the whole weight of this species was 500 shekels exactly the same as that of the myrrh. But if this be so, why is it (the quantity to be brought) expressed in halves? It is the ordinance of Scripture that it should be brought in halves only, so that the quantity may be increased by two overweights, for there was no exact balancing of the scales in weighing the spices, but a little was always added. Thus it is stated in Keritot 5a.

4וקנה בשם AND CALAMUS SPICE — i. e. cane of sweet spices. Because there are canes which do not bear sweet spices Scripture had to state (add the word) בֹשֶׂם‎

5חמשים ומאתים TWO HUNDRED AND FIFTY was the amount of its entire weight (not of the half of it as in the case of the preceding ingredient).