So how does the Supplementary Vote work again?

Today I received my ballot papers for the local elections here in Newham. Not only did I get a First Past The Post ballot paper for the three councilors for Forest Gate South ward but I also received a Supplementary Vote ballot paper for electing the Mayor.

Here in Newham the voter is asked to make three choices on one ballot paper, marking each choice with a cross, and two choices on the other ballot paper, numbering them in order of preference. I really don't think it's very workable to hold elections by different methods for the same authority. Two years ago a voter in London received a First Past The Post ballot paper for their constituency Greater London Assembly Member, an Additional Member System top-up lists ballot paper for the London wide Assembly Members, a Supplementary Vote for the Mayor of London and a Party List for the Members of the European Parliament. I'm sure there were lots of votes miscast by voters applying the rules for one system to another. Or people treating the top-up vote as a second preference - how far has this distorted the allocation of seats in the Assembly from the electorate's true desires?

And for comedy the sitting Mayor, Sir Robin Wales, states on his manifesto:

Please vote for me - No.5 on your ballot paper

Anyone who follows this advice to the letter will be casting a spoilt ballot! What's the point in using such a bizarre and confusing voting system when even the political party that introduced it can't understand it?