Depending on the type and recipe, each flavour has a different freezing and enjoyment point, depending on the fat content, sweetener and other ingredients.
As the ice cream maker only produces 500 ml of ice cream, this is normally exactly the right portion to be eaten quickly.
If you still want to keep some, you must either - as described in the instructions:
freeze it in a cold freezer and take it out of the freezer 10 minutes before eating it
or
place the ice cream in a freezer compartment that does not have such low temperatures as a chest freezer
or
adapt the ice cream recipe by increasing the sugar and fat content
or adding an emulsifier to the ice cream mixture