Why its different tho valus of memory in the same page?

I have 2 machines whit the same problem. because i don´t know what happend.

One is Linux

In this, in the clock where I see CPU load & Memory Utilization, the value of Memory Utilization is the 62 %, from 15 GB

 but when i see the Physical Memory in the section Disk Volume the Value is

 2 % for Memory Buffers

98 % of Real Memory

and

1 % of Swap Space

The 4 Values are not igual o similar.

The other is Windows

In this, in the clock where I see CPU load & Memory Utilization, the value of Memory Utilization is the 100 % ,

but when i see the Physical Memory the Value is 73 % and me Virtual Memory is 20 %. The 3 Values are not igual o similar.

So can you tell me how i can fix this or undertstand what happend?

Thanks for all