Based on the existing answers, it appears that jSUN is a receipt for supplying collateral to the JustLend ecosystem. This is why you found jSUN in your wallet after you accepted the collateral. The rules of the group are also important to keep in mind, as the group is meant to be a place for discussion related to the JustLend ecosystem and should not be used for private trading, ponzi/scam discussion, FUD, SPAM, referrals, or asking for DM. All conversations should be kept in English, and USD should be used when talking about prices. Above all, all JustLenders should be respected.