QNetworkDiskCache: cacheSize not working well

QNetworkDiskCache->cacheSize() returned values are different from size of cache directory on disk. Also, some times, both values(measured from disk and from api), are going over the values set with setMaximumCacheSize. This happens in qt 4.6 . Don't know in other versions.

Log from an application that loads web pages and monitors cache sizes:
Curent cache size from disk measures: 2698194 bytes
Curent cache size from api: 2822944 bytes
Maximum cache size from api: 3000000 bytes

Curent cache size from disk measures: 2698194 bytes
Curent cache size from api: 2822944 bytes
Maximum cache size from api: 3000000 bytes

Curent cache size from disk measures: 3049610 bytes
Curent cache size from api: 3022366 bytes
Maximum cache size from api: 3000000 bytes

This doesn't happen all the time.