Market cap is a term borrowed from the share market[1]. I don't think it's technically correct applied to BTC but it commonly is.

Market cap growth as a percentage just means, if all BTCs in circulation are worth $10bn today, and $15bn tomorrow, then the market cap has grown by 50%.

I didn't use the price of the coins themselves as BTC is being minted more slowly than DOGE.

[1] http://en.wikipedia.org/wiki/Market_capitalization

"Total dollar value" is the correct terminology for currencies

you can check the market cap for bitcoin and dogecoin here : http://coinmarketcap.com/ dogecoin is at 8 mil for now , bitcoin at 10 bil.