tpdmax-tcpdmax = 4.3-3.8 = 0.5ns not 0.8ns?
and no minimum stated for tpd.
The skew specification is the difference in propagation delay, which is
typically 0.5ns. This difference in the delay is reflected in both the typical
and maximum values of tPD and tCPD. The minimum to maximum specification in
propagation delay for both outputs is based on 6 sigma statistics of the
measurements made during the characterization of the product (over
temperature). Without even looking at the data, I'm quite certain that no
units were observed to lie at the extremes of the window that we specified.
Also, the minimum for tPD is tV (valid time). This terminology is sometimes
used to describe minimum propagation delay in logic applications. It caused
enough confusion that all recent parts have instead specified a minimum on tPD.