That's because it was trading at a level that included the class b share.

https://www.teck.com/news/news-releases/2023/teck-completes-plan-of-arrangement-introducing-a-sunset-for-dual-class-share-structure

The Class A common shares are trading on a due bill basis up to and including the Payment Date (i.e., May 19, 2023). A due bill is an entitlement attached to listed securities undergoing a material corporate action, such as the Dual Class Amendment. In this instance, the entitlement is to the new Class A common shares and Class B subordinate voting shares on the exchange of the Class A common shares. Any trades that are executed during the due bill period are flagged to ensure purchasers receive the entitlement to a new Class A common share and 0.67 of a Class B subordinate voting share per each Class A common share issuable as a result of the Dual Class Amendment. Ex-distribution trading in the Class A common shares on a post-Dual Class Amendment basis will commence on May 23, 2023, as of which date purchases of Class A common shares will no longer have the attaching entitlement. The due bill redemption date will be May 24, 2023.