@MC Thanks for reaching out and we're sorry about the confusion.
It seems as though you were shipped the wrong item or it was incomplete, as the SRAM PG950 9 speed cassette 11/34 should have 9 cogs. If you are able to go in to your local store to return it and speak with an associate about a replacement that would be best. Otherwise you can reach out to our Sales and Customer Service team at 1-800-426-4840 to talk through your return options for your order.
Again, we apologize that your item was incorrect or incomplete.