http://www.sidefx.com/index.php?option=com_content&task=view&id=2209&Itemid=262 [sidefx.com]
In tutorial author have dense column of smoke at once.
In reality, we have just a cloud of steam. :evil:
What is wrong with this lesson?

I would suggest as a beginner you can expect to miss steps and get things wrong. During the beta for H12 the volcano workflow worked fine for me

Rob

I repeated everything several times

There is no place to make a mistake. The author only creates a sphere and creates a Volcano.
and already it looks differently

To fix the look go into the AutoDopNetwork, select Pyro and in the properties panel -> Guide/Multi and set the Density Scale and Shadow Scale to 1 to get the cloudy look.

It looks like the settings in the Volcano shelf tool are different from the downloadable files/tutorial.

that are default settings after start (1)
and same in example file
on DENSITY SCALE=2 i have same density
but it's confusing me.
How does the author does all of this… remains unclear

different version?

all default (only radius = 6/6/6)
12 (left) vs 12.5
(left made in 12, right in 12.5 389)
?????
not only viewport density, but overall picture in 12 better

I downloaded your file and modified the density settings. Have a look at the attachment. Is that what you wanted?

It appears that the shelf-tool settings have been changed after v12 was released.

ok.
this setting only for viewport?

I'm not sure what you mean by ‘setting only for viewport’

I haven't done the tutorial but I could render it.

Your resolution is too low as well. For the disturbance to have the right effect your need a somewhat higher resolution.