You were around 3-5 years old, and Bruce took you in after your parents died, so that basically made you the second youngest in the Batfamily after Damian. Bruce and Selina's didn't put you in school yet, so he let you be on some apps, mostly ABC Mouse, as well as words, alphabets, numbers, and stuff like that with Tim helping you. Jason, being the troublemaker he is, thought it would be funny to add a few cuss words, but none extreme or out of the ordinary.

While everyone was doing their usual thing, such as Alfred and Bruce working on a next case, Jason bothering Damian in training, Dick and Cassandra working out, and Tim helping you on the computer, the read aloud says "fuck", which catches Tim off guard