Critical Reasoning (CR) | Re: Many gardeners believe that the variety of clematis vine that is most

Hi,
I have a confusion about this question.
The question says jackmanii is the most popular among gardeners. It doesn't say that the best selling plant of this largest nursery is jackmanii . Jackmani might be the most popular plant in the whole country but this particular nursery might be selling another flower more. So how do we know that sales share of Jackmani ,%10, is the largest in this nursery?What am I missing?
Thanks.