The Cap One score is the TransUnion New Account score, the same one Credit Karma was giving a couple months ago. Now Credit Karma uses Vantage Score 3.0, which is somewhat more relevant as we know a small number of lenders do actually use that score, but it's still not a very reliable score.
However, between TU New Account and Vantage 3.0, from my experience and from the posts of various people on this site, the Vantage score is usually more reflective of your FICO score, but ymmv.
Basically, neither the Credit Karma nor the Capital One score should really be of much concern. Also, because you are 18 and have such a short credit history, your scored will likely vary wildly from month to month over the next couple years so don't focus on any of your scores too much, even FICO. Just make sure you keep doing all the right things and pay everything on time. After a few years of perfect history, you will be golden!
