According to Jim Recap: The Tale of the Tape (Part 1)
Now that Ryan and Dana are married, he is constantly making these little romantic gestures all the time that are making Jim look bad. The latest is to get Dana a bottle of champagne (that appears to be Dom Perignon) and 118 yellow roses (118 because that was the amount of the dinner tab on their first date). The only mistake he makes is to tell Jim that they are waiting at the house.
This is a mistake because before Dana gets home, Jim and Andy head over and steal them, and Jim and Cheryl have a nice romantic evening at home with champagne and 118 yellow roses.
Ryan made one other mistake, and that is to tell Dana that the champagne and roses were waiting, so when she sees Cheryl's roses, she asks how many, and once again, Jim is busted. But he has a secret weapon - the mix tape.
Early on in Jim and Cheryl's relationship, Cheryl gave Jim a mix tape of classic music and it's been with them ever since, for every significant moment. Cheryl thought the tape had burned up in a fire (which Jim set to cover for another scheme). But really, Jim has been saving the tape in his toolbox, and now is the time to bring it out. The only problem he has is that they don't have a tape player. So he gets it remade into a CD, where they boost all the levels - it sounds great.
When Cheryl and Dana are listening to the new CD later, they hear a message that was never audible before. It says "I love you, Cheryl". Unfortunately, that wouldn't be there if Cheryl made the tape for Jim, and another secret comes out - Cheryl didn't make the tape for Jim. Cheryl's ex-boyfriend Chad made it for her, and Jim just happened to stumble across it and assumed she made it for him. She didn't have the heart to tell him the truth.
So that he doesn't hear it, she destroys the CD in the blender.
Make sure you read about the conclusion in The Tale of the Tape (Part 2).
