Olivia is frustrated with the administration because they only allow the library to be open for a short amount of time. She rightly notes that it doesn’t actually cost anything for the library to be open longer, partly because her salary is paid regardless of the number of hours. The administration, though, has used the money for personal reasons and doesn’t understand why it needs to be open longer. Olivia argues that the marginal cost of operating the library is zero, which implies that operating the library is only one large fixed cost.
Thanks to Brittany Pifer for the scene recommendation!