450 credits (rounding off) for 15.5 hours. That's rather low. 29 credits an hour? That's more on par with Android clients. Actually, I think I get that in less time than that on Android.

It's hard to compare apples and pears, as BOINC tries its best to do with the credit system. I've just started with C@H and my laptop which is my trial machine for projects completes a camb_boinc2docker job in about 9 minutes with all four virtual cores (i7-7500U). That's ~30 cpu minutes for ~30 credits or 60 credits per hour. Double what you describe but I don't know what hardware you're running on nor which application it was.

Anyway - try focusing on what's important. What those 15.5 CPU hours does to progress our understanding of the cosmos! If it's 450 or 45000 "credits" is of less relevance.:) (But I know - big integers ARE fun, no matter what people tell us!)