Can QHash::capacity() be smaller than QHash::size()?!?

[iw2nhl]

I'm trying to optimize memory usage in my code.
I found that some Qt containers have capacity(), reserve() and squeeze() functions for this purpose.
Making some tests I found a strange result (among normal ones!):
in some conditions I get capacity() < size().
If I understand correctly the documentation, capacity() should give the number of allocated items (which generally is greater than the number of inserted items, for speed reasons).

QHash< DataUniqueId, DrawItem* > m_lookupTable;
 
// Insert data into m_lookupTable
for (...) {
    m_lookupTable.insert(..., ...);
}
 
qDebug() << m_lookupTable.size() << m_lookupTable.capacity();
 
// No more insertions, so release any unused memory
m_lookupTable.squeeze();
 
qDebug() << m_lookupTable.size() << m_lookupTable.capacity();

QHash< DataUniqueId, DrawItem* > m_lookupTable;

// Insert data into m_lookupTable
for (...) {
    m_lookupTable.insert(..., ...);
}

qDebug() << m_lookupTable.size() << m_lookupTable.capacity();

// No more insertions, so release any unused memory
m_lookupTable.squeeze();

qDebug() << m_lookupTable.size() << m_lookupTable.capacity();

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This is the output:

500 521
500 257

500 521
500 257

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As you can see, after the squeeze(), size() > capacity().
How can the number of allocated items be less than the number of real items?
Am I doing something wrong?

Thanks in advance,
Alessandro