The setting "System monitor width" exist, but not "System monitor height".
It is needed since the panel height can be increased in MATE: gsettings set org.mate.panel.toplevel:/org/mate/panel/toplevels/top/ size 55
Ideally, automatically set "System monitor height" to org.mate.panel.toplevel:/org/mate/panel/toplevels/top/
See this issue on Launchpad: https://bugs.launchpad.net/indicator-multiload/+bug/2028991