Similar to Jack-Jack Attack, the short details events taking place off-screen during the main film's story. In this case, it shows us the night Edna spent with Jack Jack while Bob caught up on some much needed rest.
Edna is fascinated by studying and recording Jack Jack's various superpowers. Things start out smoothly but as the night progresses it goes off the rails when she triggers Jack Jack's Demon Imp form due to running out of cookies which forces her to take refuge in her costume demonstration room.
However, once Jack Jack exhausts himself and falls asleep, Edna sets to work designing him a red supersuit (similar to the ones worn by the rest of the Parr family) that can monitor and, to some degree, contain his various powers.
When Bob returns to collect Jack Jack, Edna informs him that the cost for the suit will be covered by her fee being the EXCLUSIVE designer for Mr. Incredible, Elastigirl and Frozone throughout the known universe and until the end of time... however, babysitting Jack Jack is something she did for free.
After Bob leaves, Edna notices Jack-Jack has teleported next to her (since his head wasn't visible in the car when it pulled away), and Edna calls out to "Robert" as she chases after him carrying Jack Jack.
