Is Salesforce API limit on outbound or inbound?

Unfortunately your test is flawed. What you're missing here is that using the Developer Console uses API calls to the Tooling API (it's a little crazy that these are counted, I know)!

The API call limit includes inbound calls only. Outbound calls (i.e. callouts) are only governed by the per transaction and maximum timeout limits.

The Salesforce Developer Limits Quick Reference should contain all the information you need.