It's the idea that in a radio ad you can't charge a Conservative Party or a Liberal Party more or less based on which political party it is. That has to be offered at the same rate, at the lowest possible rate available, as follows:
a rate for an advertisement in a periodical publication published or distributed and made public in the period referred to in paragraph (a) that exceeds the lowest rate charged by the person for an equal amount of equivalent advertising space in the same issue of the periodical, publication or in any other issue of it that is published or distributed and made public in that period.
It has to be the same rate, the same lowest possible rate, within that publication.