QFontMetrics::height() is not ascent() + descent() like stated

Documentation for Qt 5.12.2 states that QFontMetrics::height() is not ascent() + descent() however this is not the case:

int letterHeight = QFontMetrics(mpHost->mDisplayFont).height();
int capHeight = QFontMetrics(mpHost->mDisplayFont).capHeight();
int ascent = QFontMetrics(mpHost->mDisplayFont).capHeight();
int descent = QFontMetrics(mpHost->mDisplayFont).capHeight();
int ownLetterHeight = ascent+descent;
qDebug() << "letterHeight:" << letterHeight << "ownLetterHeight:"<<ownLetterHeight<< "capHeight:" << capHeight << "ascent:" << ascent <<"descent:"<<descent;

// letterHeight: 51 ownLetterHeight: 62 capHeight: 31 ascent: 31 descent: 31

Using Bistream Vera Sans Mono with font height 12.