GGplot is drawing the wrong y axis for 'counts' in histogram

Question

 ggplot(data.frame(dat<-round(rnorm(1000),2)),aes(dat)) +
 geom_freqpoly()+ geom_point(aes(x=-0.78,
 y=sum(dat==-0.78)),colour="red",shape=18,size=6)

I drew this plot and when i checked how many times -0.78 occurs by using sum(dat==-0.78) , it said it occurs 3 times. But according to the plot -0.78 occurs more than 50 times(the y axis is counts). This seems wrong to me. The following is the plot. If the number occurs 3 times in my data then why does my plot say it occurs more than 50 times?