I believe its a paragraph or two of how the parents met, the birth of your character, then significant life events such as first sign of magic, and other things that happened to shape who your character is/was/is going to be. Then after that it is really just each year of school. You can add more than that if you want to. As well, depending on how old your character is, you might want to add a paragraph or two about how your character felt/what they did during the events of the HP series.
Your RP sample should be at least two paragraphs, be written in third person.. Use
@Elias Deyer's as an example or
@Volya Nikolov's. I really dunno how to explain it, but it shouldn't have dialogue between two characters in it, and be written from the view of your character? If that makes sense?
If you need more examples of either, just click on peoples profiles. Use them as a guideline, but don't feel like you need to have absolutely everything in there. Also writing more is alwaysss encouraged! <33
@Kevin410