AD9959 IO update question

Hello all. On page 30 of the AD9959 pdf - there is information involving IO Update.

Can I ask if there might be an error with that information?

For the original diagram of Fig. 40, I can see that --- if the IO UPDATE voltage is HIGH and when a rising edge from SYNC_CLK occurs, then that will be point 'A' on the diagram, which represents 'registration' (preparation) of the data in the I/O buffers. Then, at the next rising edge of SYNC_CLK (which marks point 'B'), the contents of the I/O buffers is then transferred to a relevant AD9959 data register.

For the original diagram of Fig. 40, it can be seen that the activity at 'A' and 'B' occurs when the data contained in the 'BUFFER' (ie. bottom of the diagram) is "N+1".

So, when event 'B' occurs, the Data Register (second-last row of Fig. 40) should take in (ie. read in) the contents "N+1", instead of reading in contents at "N", right?

The I/O buffer contents represents the beginning of the journey, while the data register represents the destination (or end) of the journey, right?

Thanks all.

minor edit
[edited by: KennyL at 11:46 PM (GMT 0) on 13 Oct 2019]