When you post up a picture you can get an explanation of the rating system. Copy and pasted here for convenience. :)
Ratings on JaxPad
JaxPad ratings are helpful for filtering content that people may not want to see. Below is a guide to follow for applying ratings to artwork:
* G - No violence or sexual situations.
* PG - Suggestive situations implying violence or sex.
* PG13 - Mild nudity (no "below the belt" frontal, must be non-sexual and not the focus, etc.), bloodless violence and mild language.
Don't fret too much. As usual, err on the side of caution. If an image is flagged many times as being misrated, we will investigate and may bump the rating up a notch. No harm, no foul. Even if an image is removed, we do not hold it against you.
However, if the image is blatantly misrated, i.e. set G for an PG13 or above picture, we will change the rating appropriately and warn the user. Multiple instances might result in gallery privileges being revoked. Don't make us take out our ruler!
If you have any questions regarding this, please ask us.