For example if btc's rate is $45,000/btc right now, and you bought 1 btc, and later the rate becomes $46,000, it would show you $1,000.
And if it's $44,000, it would show you $-1,000...and so on.
Something like this...

On my previous take with an app, I don't exactly rely with profit monitoring but I do prefer real time updates given from that app I used to have. I'm using crypto tracker app from playstore, and the results was overwhelming now I can closely monitor my asset, the also I could project other assets that was starting to rise and fall.
Please take a look on this link:
https://play.google.com/store/apps/details?id=com.coinstats.crypto.portfolio