To understand this question we need to consider what happens in Scene Four as a whole and think about how it relates to this tedious job that Amanda is shown to work at during the play at various stages. Let us remember that it is in this scene that Amanda tries to convince Tom to find a suitable friend who could marry Laura so that she can be saved from spinsterdom and can be provided for. Key to this talk that Amanda has with her son is the following speech:
I know your ambitions do not lie in the warehouse, that like everybody in the whole world--you've had to--make sacrifices, but--Tom--Tom--life's not easy, it calls for--Spartan endurance!
Amanda herself shows her own "Spartan endurance" by working hard at a job that requires her to demean herself by calling a series of women to get them to subscribe to a magazine and talking to them about their kidney conditions. This of course is not what she would have wished or expected from her life, but the scene ends this way to show her resolution, but also their economic situation.