Okay, got through! I got transferred a couple of times, so if anyone’s also dealing with this problem, the number to call is +886 2 2388 9393 ext 2361.
jimbob132 was right; they wanted me to document entries into China. I didn’t 100% understand what they were saying, due to lack of fluency, so to be safe I took pictures of every visa page in my passport to show that the trips I mentioned were the only trips I took.
They didn’t tell me to dig up my expired passport to find previous trips; I think it’s because my passport is from 2011 the trips I took were in 2016 and 2018 (i.e., more than 4 years later), but again I can’t be certain.