The code is written as follows:
a<-ggplot(data = dec05,
aes(x = Month, y = Adjusted.Passenger.Count),fill='white') +
geom_bar(stat = 'identity')+labs(x=' 2005') +
theme(aspect.ratio = 2/1) +
geom_col() +
geom_text(aes(label = Adjusted.Passenger.Count),
colour='red',vjust=-0.2)