Often during a Rack and Return, one barrel will end up being a partial. This barrel can be topped off either with the same lot or a different lot to fill it.
A top off cannot be completed within a Rack and Return task or action and must be completed as a second task or action after the original Rack and Return is submitted.
After completing a Rack and Return, use the Transfer function to move any amount of wine from any lot to that partial barrel. This is different from the "Topping" function, which does not change the contents of the barrel being topped.