The chart is a type of HRD, except that the spectral type axis has been replaced by the mass axis.
<br>
The greater the mass of a star is, the faster it burns its hydrogen. The brightness of this giant star is therefore larger than in smaller stars.
Therefore these giant stars are not very old. Only some ten thousand years are called O-stars and up to 200 billion years so-called red dwarfs (M stars) old.