Ad Links search box: does it count as an impression?

...and is this unlike PSAs on standard AdSense units?

[ProTalker]

Would I be correct in assuming that if a PSA is shown for standard AdSense units, it's not recorded as an impression in the AdSense reports, but if a "search box" is shown for Ad Links (the equivalent of PSAs), then it is recorded as an impression?

The reason I ask is because my pages containing Ad Links and standard AdSense units are currently showing fairly significant differences (around 10%) in the page impressions for the two styles, and with every page having both styles, the impressions should be the same.

[jetteroheller]

As I see in my stats:

I have many pages with 120x90 and 300x250 recorded in seperate channels.

The channels with the 120x90 AdLink shows always higher numbers.

I assume this is because

An AdLink showing search for ads counts as an impression
A 300x250 showing my PSA replacement does not count