Facebook does not explicitly states number of API calls, or anything else regarding rate limits of their Ads API at https://developers.facebook.com/docs/reference/ads-api/api-rate-limiting/
Is there another page that specifies it? Have you empirically measured what the rate limits are?
No, they do not specify the actual rate limits anywhere sadly. Just how long you have to wait till you can request again when you've hit the limit (Graph User: 30 minutes, Ads User: 1 minute).
You can measure the rate limits, but they will differ from time to time as Facebook itself grants a score (which we can't retrieve) to the API call when you make it.