Vector of (Structs having vector)

The following piece of code as stated in Bjarne Stroustroup's C++: Programming and Principles

struct Day {
    vector <double> hour { vector <double> (24,-7777)}
};
struct Month {
    vector <Day> day {32};
};

This piece of code initializes 32 days, each day as a vector of 24 hours initialized with -7777;

The question is why list initializer {32} creates 32 days. Isn't it supposed to initialize day vector with 32 as a initial value instead of creating 32 members?