Author here: Sorry for the confusing formatting on the task descriptions at the end of the paper. That "4" is the human-generated target completion, not a model generated completion. I'm not sure whether the model got that particular question correct, but from Table 3.7 that GPT-3 has 36.5% accuracy on DROP in the few-shot setting.
Many other readers were confused by this so we'll update the formatting to say "target completion" to make this more clear.