If someone asks you to "sum an array" then it's quite reasonable to think they mean calculate the sum of an array. Some languages (PHP springs to mind) have native "array_sum" functions. Wondering if someone from Google, who is interviewing a developer means "sum or summarize" would be weird.
Yep I guessed. And that's a good thing. But they should make sure the call environment is optimal (good reception, no background noise, ...) and the interviewer sounds eager to receive questions.