R Studio: Numerical Example where qnorm() and pnorm() are not exact inverses?

#1
This is a question in one of my question books. It states that R's numerics have a slight numerical inaccuracy.
pnorm() and qnorm() are functionally inverses, but this questions asks for an example where it shows they are not exact inverses. Ideas?
 
#2
Code:
x <- 1:15

p <- pnorm(x, mean = 5, sd=2)
p

x2 <- qnorm(p, mean = 5, sd=2 )
x2

x- x2
[1]  0.000000e+00 -4.440892e-16  0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00  0.000000e+00
[8]  0.000000e+00  0.000000e+00  3.552714e-15  7.105427e-15  3.375078e-14  0.000000e+00  1.083578e-12
[15]  5.964829e-11
You are correct. They are not exact. But I must say that I am impressed by their accuracy.