interpreting free cmd output

Hello experts,
I know this is a much discussed topic, but need help to understand what do we interpret of the below:

bash-4.1$ free -m
              total       used       free     shared    buffers     cached
 Mem:         64300      63914        385        183        694       7058
 -/+ buffers/cache:      56161       8139
 Swap:        31999         63      31936

The server has 64GB RAM. 20GB is allocated to Oracle as SGA. And there are about 100 Oracle server processes and its running RAC, so lets take another 2GB. In above output, cached is 7-8GB.
How can I find where is the rest being used? We have verified multiple times and there is nothing else running on the server except Oracle server.

Swap is a partition on the disk, so that 31999 is not a part of 64GB.

Transparent Huge Pages is disabled, Huge Pages is enabled and

vm.nr_hugepages

Many Thanks