Sforno on Exodus 30:34/ספורנו על שמות ל׳:ל״ד

1קח לך סמים, the ones already mentioned in connection with the oil of anointing in verse 23-24 plus the three mentioned in this verse, i.e. נטף, שחלה, חלבנה, and in addition to these some other spices known to act as improving the mixture of those already listed. According to our sages in Keritut 6 Shibbolet, Nerd, Karkom and Kosht were such spices which when blended in with the ones listed in the Torah already would provide the balance of fragrance the Torah wanted to achieve. [The problem facing commentators is the fact that even when we add all the spices or oils mentioned in this chapter together, even assuming that frankincense is one of them, we only arrive at a total of eight, whereas traditionally there were supposed to be 11 as we mention in our daily prayer of Pittum haketoret. Ed.]

2ולבונה זכה, this pure frankincense did not need to be mixed with any other ingredient to achieve the Torah’s purpose as part of the incense. This helps us arrive at the number 11 our sages state were contained in the mixture presented on the golden altar.