The fixed length values region stores two things. Either values fitting into the 8 bytes - called fixed length values like long, double, or int - or in the event the value of a particular field doesn't fit into that chunk only a pointer or a reference is stored. This reference points to a byte offset in the variable length values region. In addition to the pointer, the length (in bytes) of that field is also stored. Both integer values are combined into a long value. This way, two 4-byte integer values are stored in one 8-byte field. Again, since the number of fields is known, this region is of variable length and reserves 8 bytes for each field.