This is a integer field on some table. You should try this for now:
function onChange(control, oldValue, newValue, isLoading, isTemplate) {
if (isLoading || newValue === '') {
return;
}
if (!Number(newValue) || !Number(oldValue)) {
var msg = "Maximum waiting time should be Number " + newValue;
g_form.hideErrorBox('max_waiting_time');
g_form.showErrorBox('max_waiting_time', msg);
}
}
You can refer https://www.servicenow.com/community/developer-forum/how-to-use-getmessage-quot-message-key-quot-in-... for dynamic newValue.
Also, add the key of your getMessage in the "Message" field on your client script. If this field is not on form use list view on client script to update this.
