Arria 10 DSP 18×18 Sum of 2 Mode

I am looking at the

Intel® Arria® 10 Native Fixed PointDSP IP Core User Guide

ug-01163

2017.03.13 https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/ug/ug_nfp_dsp.pdf

On page 14, it indicates the equation for the 18x18 Sum of 2 mode is

resulta =[±(ax * ay) + (bx * by)]

Looking at the block diagram in Figure 3, I think it should be:

resulta =[±(ax * (ay ± az)) ± (bx * (by ± bz))]

Is that correct, or is there an error in the block diagram?

Also, what is the significance of white blocks or dotted blocks in the block diagram?

For instance, does the negate function exist in this mode (it is white)?

Thanks