On a balanced split, roughly 5 misses in Reading and Writing and 5 in Math, which is 750 per section. Five per section, with the harder Module 2 required in both. At this level most remaining misses are careless errors rather than gaps in content knowledge.
The split matters as much as the total. Because the two sections scale differently, five misses concentrated in one section will not land at 1500 the way a balanced five-and-five will. If your practice scores sit just under, look at which section is carrying the deficit before adding study hours to both.
The full picture, with the surrounding detail, is in Is 1500 a Good SAT Score? In Range at Every College.