They will send up to the unit, however if you are not around, they will drop it into the letter box. If it does not fit, they will send it back to singpost. A redelivery can be rearrange if needed via singpost website if needed, if that happens, you should receive a collection slip in your letter box. Hope this helps.
They should drop it in the letter box, if it does not fit into the letter and if no one is around, there should be a slip of paper for you to request redelivery or collect it at the post :) let me know if you need more help alright