Black-Scholes model – value option

Hi. I have a question regarding value call option and N(d) e.g

d1= 0.6
d2=0.4

N(d1)= 0.5 + 0.2257 = 0.7257
N(d2) = 0.5 – 0.1554 = 0.3446.

Are my calculations of N(d2) correct? Or it should be also “+” (0.5+0.1554?)
Maybe I do not understand it correctly or there is a mistake in the book..

Thank you for the help.
Angelika