Miss Pross' comment about "hundreds of people," in Charles Dickens' novel, A Tale of Two Cities, literally refers to the sounds of footsteps passing by their home, and the noise from the foot traffic that, through some strange acoustical phenomenon, sounds as if the Manette house is receiving hundreds of visitors.
In Chapter Six: "Hundreds of People", of the Second Book: "The Golden Thread," Mr. Lorry visits the family and he, the Manettes, Miss Pross, Darnay and Carton enjoy a pleasant evening. However, Miss Pross' comment about the hundreds of people continues to puzzle Mr. Lorry. Literally, it sounds like many people are rushing to see them.
In terms of the figure of speech it represents, it is exaggeration and called hyperbole. The phrase has two functions, and, as used, it is also the literary device technique of foreshadowing. So Miss Pross' tendency for exaggeration--hyperbole--foreshadows upcoming events.
Dr. L. Kip Wheeler describes foreshadowing as:
Suggesting, hinting, indicating, or showing what will occur later in a narrative. Foreshadowing often provides hints about what will happen next…Often this foreshadowing takes the form of a noteworthy coincidence or appears in a verbal echo of dialogue.
Foreshadowing is something that is often not noticeable until the event it hints at has passed and one can look back to see that a clue had been left regarding this event. In this case, at the time this chapter is unfolding, thoughts of the recent trial are fading, and this particular evening is a welcome interlude; even Mr. Lorry is thankful to have found himself a part of this family.
eNotes.com's analysis of this chapter reveals:
There is a sense of normality and quietness to this chapter, but hints are given that this quiet normalcy is about to be shattered.
Other examples of impending "disaster" are seen in Dr. Manette's inability to put his memories of his time in prison aside; his strange look at Darnay which is reflective of the secret knowledge Manette harbors about the younger man; and, the rushing sounds of footsteps that build to a crescendo in the midst of a fierce storm of thunder and lightning will point to the future developments of the French Revolution, and how they will be played out and affect the Manette family and their circle of close friends.
The echoing footsteps are an obvious foreshadowing that something involving crowds of people is about to happen. And the coming storm can be seen as yet another symbol of trouble to come. The final paragraph of this chapter further shows that something ominous is bearing down on the people in Dr. Manette’s house.