Lottery is a slow product: a player buys a ticket and then waits a day, or a week. Mini games exist to fill that gap - quick rounds with an instant result, played from the same wallet.
They can run on the main balance or on a separate bonus balance, which is the usual setup: bonus credit earned elsewhere on the site becomes something to spend immediately, and the player comes back to the tab instead of leaving after the purchase.
Find them on the homepage under Mini games.