Sometime, we come across an issue where VIM only occupies just part of the available terminal screen space. We usually encounter this issue when we ‘ssh‘ into a remote machine and run VIM. This is because the terminal reported wrong number of rows and columns to the VIM editor.
As a fix for this issue, execute the command: ‘resize‘ (without quotes) on the terminal prompt and rerun VIM.
Reference:
A Quest for Knowledge 
I would also recommend adding the line ‘resize &>/dev/null’ to .bashrc or .profile or .bash_profile in your home directory so that anytime you log into a machine using ‘ssh’, VIM or other command will never assume a wrong row or column number.