anchor.diff:      // root page
       // age
       // number of pairs
  -    // each pair is startBlock,lastBlock
  +    // each pair is startBlock,countBlocks
       // all in varints
   
       let writeHeader hdr =
  
positive.code:             else
                  let size = settings.PagesPerBlock
                  let newBlk = PageBlock(nextPage, nextPage+size-1) 
                  nextPage <- nextPage + size + WASTE_PAGES_AFTER_EACH_BLOCK
                  //printfn "newBlk: %A" newBlk
                  newBlk
              )
  
negative.code:     let fsMine = io.OpenForWriting()
  
      let HEADER_SIZE_IN_BYTES = 4096
  
      let readHeader() =
          let read() =
  