Goodness of fit test for a normal ditribution

#1
In the example from a site I was trying out http://www.cimt.plymouth.ac.uk/projects/mepres/alevel/fstats_ch5.pdf this problem
in page 107 about Goodness of fit test for a normal distribution.Question is about analysis of fat content of hambergers.

I understand that we need to have the two intervals -infinity< x< 26 and 40< x<infinity to find the class probabilities of intervals
26< x <28 and
38< x<40.
But why should the expected frequencies of the two intervals -infinity< x< 26 and 40< x<infinity be also calculated and used for chi Squared value ?
These two categories are not there in the given data set.

Is it necessary to break our intervals such that they start from -infinity and end from infinity as this is a normal distribution?