Available memory calc incorrectly.

Available memory calc incorrectly.

Available memory 1.27 GB
Total memory 1 GB

```
# free -V
free from procps-ng 3.3.16

# free -b
              total        used        free      shared  buff/cache   available
Mem:     1073741824    72876032   640540672     1249280   360325120  1000865792
Swap:    1610612736           0  1610612736
```

LXC / Ubuntu 20.04 LTS