about magnitude affected by atmospheric extinction

I put the star Zavijava (beta Vir) sao 119076, etc. a degree above the horizon. (h = 1° apparent). The magnitude of the star is 3.55 reduced to 6.97 by 26.24 air masses. This means that the star loses approximately 3.5 magnitudes. Is that correct? 6.97 is the magnitude with which I would see the star? If so, I cannot understand, because in this page:
http://www.icq.eps.harvard.edu/ICQExtinct.html
there is a table showing "Average" Atmospheric Extinction in Magnitudes and I found for h=1° (or z=89°) 7.38 mag.
88 5.41
89 7.38
 90 11.24
Does this mean that I should add this value to the magnitude of the Star? In the case of the example we have: 3.55+7.38 with a result of 10.93 mag.
thank you