This is not a jab at you (or your book), But I always assumed O'Reilly's per book sales would be significantly larger, like 4 figures at the minimum
I've known a few authors who published with O'Reilly and other major publishers and most told me that they made less than minimum wage in the end. There were other benefits, such as increased name recognition and credibility that let them charge more as consultants, but the direct proceeds from writing a technical book seldom paid off even two decades ago.