I had 2 banners active 10.9-30.9 in same spot, in header section. ACP says one of them had 553719 impresions in that time. BUT, Google analytics says whole site had 163 154 page views in that time. Something isnt quite right in here. What do i tell to customer about impressions?

Both values could be right at the same time. I would check your server stats in comparison. 

There is HUGE gap in those. If i sell advertiments, i have to rely on GA stats, i cant say "IPB ACP says you got 10 times more impressions than GA says".

They are measuring totally different things. An ad spot view is counted when there is a view of that ad spot. Google Analytics is something very different. It’s supposed to show visitors of your site. It will usually exclude bot activity, it will not fire for anyone or any bot which blocks JavaScript in general or Google services in particular. And so on. 

Again: Check your server stats. They reliably measure what what actually requested and delivered. 

1 minute ago, opentype said:

It’s supposed to show visitors of your site. It will usually exclude bot activity, it will not fire for anyone or any bot which blocks JavaScript in general or Google services in particular. And so on.

So GA stats are more accurate to customer. They dont care about bot views or visitors with adblocker.

Yeap, same experience as me: 

 

If you believe you are experiencing a bug please submit a ticket in your client area. The hit counter is a very basic function - advertisement is loaded and displayed, we increment the counter by 1. Without more details it's hard to determine why you might believe you are seeing invalid values here.

34 minutes ago, bfarber said:

If you believe you are experiencing a bug please submit a ticket in your client area. 

@bfarber See ticket #1021226. (and this topic)