Task 4.11 - Filtering with Standard Access-Lists

Hi

This task question: Configure a one line standard access-list on R6 to filter out all routes coming from BB1 that have an even number in the third octet.

This task answer: access-list 1 permit 0.0.1.0 255.255.254.255

I know the answer is referring to the 3rd octet placement but not sure why does the even number means 1.

Since this is for even number then what about if the question is asking for the odd number? What will it be then? Appreciate if any experts can enlighten me on this by showing some examples. Thanks.