I'd agree on the surface with the comments above, but also say its possible that there was a reason (or multiple) for this. If you have significant concerns, I'd ask someone from the installation company to walk you through their measuring methodology as it applies here. A few possibilities: - Racked opening. You can see that the gaps are large in two corners and smaller in the other two. While a uniform 1/4" gap would be great, its rare in practice, especially in older homes. - Stepped jamb. Looks like there was an internally hinged unit in there previously, those often have a step in the jamb where the panel closes against. The gap on the face would look much larger than the gap at the smallest point in those cases. Its also possible that there was a step/stop of some sort that they couldn't definitively deterimine whether or not it would be able to be removed at the time of measure. We see striaght through on the side in your measurement shot, but we don't know what that looked like before, or what the other sides looked like. - They may have planned for a buck frame (generally a 3/4" wood frame) but in the end there wasn't clearance for it. - As far as being secured, ideally there would be shims placed on the other sides as well, however that isn't always done in practice. If this is still in progress it wouldn't be out of line to ask for it. The installer may say that the foam offers support and locks the window in place which is not lying, but shims would be best practice. - As far as finishing, was interior finish part of the scope of work? Typically it would be, I'd imagine that they would add some sort of finishing piece to cover up the gap/foam and make it look complete. At the end of the day, based only on these pictures, it looks to me like the only thing that you will really lose here is 1/4-1/2" of glass on each side of the window. That said, again, I'd definitely have a talk with them about why the gap appears to be so large and go from there.

Thanks everyone for the condolences. I can only write from one platform these days. And it's sketchy at best. Stephanie that is good news that EVS show something similar. It's just so hard to say since most folks post pics when the disease looks progressed. I often wonder how long they have been infected to get the typical witches broom. Here are a few more from today of the same growth.

I can't stand the semantical games played with stone. It looks natural, however, if you can feel it, it's gonna catch crud. When it does, it will become contaminated and more pronounced. Since they've filled it with epoxy, although I don't know how you'd get epoxy thin enough to penetrate, maybe they can abrade it to flush. Good luck; I wouldn't worry about it.

I put these stainless gap fillers on either side of my range, they look fine and protect the counters. Bonus no crumbs go down the sides! https://www.amazon.com/Countertop-Kitchen-Between-Counter-Stainless/dp/B09JFHT2Y8/ref=sr_1_2_sspa?crid=CGRO2PDOW1A3&keywords=stainless+steel+counter+trim&qid=1644767192&sprefix=Stainless+steel+counter,aps,88&sr=8-2-spons&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUE1MTQ3OVQ5U1NXQTgmZW5jcnlwdGVkSWQ9QTA0ODk4NjYxUTZDQ1RaWElaRzdZJmVuY3J5cHRlZEFkSWQ9QTAwNDExNjMxTVdNUkNRM0E5NUpKJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1