Based on pictures and comments, you've got a 200A Square D QO panel. The invoice said 150A Cutler Hammer or QO. I think the invoice is, for better or worse, a generic "heavy up whatever" statement that means "we'll put in at least 150A panel of one of these two major good quality types of panels".
It may be that this company does so many heavy-ups that barring extras like solar hookups they just have a few boilerplate prices - 150A-250A CH/QO, maybe <150A CH/QO, maybe 250A+ CH/QO (i.e., for the class 320/400 double 200A panels) and maybe a low-ball BR/Homeline price when they're hungry.
It seems a little odd to me for electrical because there are so many variables. But sometimes easier than keeping track of all the little details. Similar to when I had a hot water tank replacement last year - I sent them pictures, they sent me an all-inclusive flat price, and they didn't itemize the expansion tank, fittings, valves, etc.
That's a 40 or 42 space QO panel. Wouldn't be out of place in the Tesla Gigafactory, as it's one of two industrial-tier panels in the consumer market (the other being Eaton CH aka Cutler Hammer). And they went for the largest number of spaces generally available at sane cost, which is what we recommend.
Square D doesn't make 40/42s with 150A busing. I don't think anyone does, because it would be a separate SKU and an odd duck product that no distributor would want to stock, only to save 40 cents a unit of copper or a nickel of aluminum. Panels of this size generally have 200A or 225A busing.
If you're after solar, that'll give you 40A or 70A of solar, respectively.
I don't know why they wrote 150A+ given their intentions of giving you this panel.