It's not really a "blackout"... I guess it's actually kind of hard to describe.
Have you ever tried to read a sentence and listen to someone talk at the exact same time? You are only going to be able to "focus" on one or the other, or you'll fail and understand neither of them.
Without medication (and on bad days) my entire life is like there is a second part of my brain that is vying for my attention. Either focusing on something not important (hey i never noticed his hat, did he always have that? I think he did in the beginning... Oh shit I missed what's happening again), or in many cases focusing on the act of trying to focus that I forget what I'm actually supposed to be focusing on (and then the pity party in my head starts about how pointless it is to even try here right now, and that then is a 3rd distraction).
There's also times that I can hear and understand what is happening, but everything from about 3 seconds ago is just... gone... So I can read and fully comprehend a sentence, but I'm trying so hard to focus on that sentence that I don't commit the previous one to memory, and any references back to it get confusing because I don't remember what happened there.
Interestingly that last one happens most with the 6 digit 2-factor authentication codes. I break them up into 2 sets of 3, but when i've said the second set of 3 to myself to try and remember the whole string long enough to switch apps and enter it, I've forgotten the first 3...
Like most things, it's not as bad at some days and times, and worse on others.