Measure it yourself with a stopwatch.  Be sure to calibrate your
speedometer for an accurate 60mph indication.

There are too many variables for the literature to provide you with a true
spec.  Some are:

wind
temperature
octane
atmospheric pressure
altitude
grade
surface conditions
tires
fuel load
state of tune
cheating by the manufacturer

You might question cheating, but they do cheat.  Their 0 - 60 is with a
minimum load and on a cold day near sea level.  A better test is with
maximum gross weight the vehicle is certified for.  What good is to have a
0 - 60 time of say 11 seconds when its more like 20 seconds when you load
it up with your family and vacation baggage and head for the mountains?
You don't want to be surprised when you try to overtake on a hot day with a
fully loaded van to find out it runs into an invisible block wall at 70 mph
or even less.