Let's recall cribbage scoring, rules and the the combinations that give points: 15: Any combination of cards adding up to 15 pips scores 2 points.
In explanation below we use card notation of all our card games, 'Suit Value', DJ means Jack of Diamonds, S0 means 10 of Spades etc. Of course, in online cribbage it is done already. To simplify calculation, order your cribbage hand left to right from low cards to high. Muggins is when a person misses points and the other person takes them. Moreover, you can select the 'Manual' option or play non-online cribbage with Muggins variation. Though in online cribbage you don't need to score manually the counting your cribbage hand correctly is a very important part of the game of Cribbage.