Yes the time shown on the API documentation page is the TTL in the cache – so it’s the minimum time between refreshes of data. (You can see more detail about cache hits/misses and age etc. if you examine the HTTP headers in each each response, see below). As for quotas, unfortunately they are not currently made visible for the user accounts on https://api-portal.tfl.gov.uk.
Contact us if you are having issues with quota limits.
Relevant caching headers from Varnish:
curl -I "https://api.tfl.gov.uk/StopPoint/940GZZLUVIC"
HTTP/1.1 200 OK
Cache-Control: public, must-revalidate, max-age=43200, s-maxage=86400
Via: 1.1 varnish
X-Cacheable: Yes. Cacheable