@Eccup Reservoir Apologies for late response. You can create alert by providing below information.
Under Measurement
Measure - Table rows (The output of the ARG query will be some no. of rows)
Aggregation type - Count (Count of rows in the output of the ARG query) - for example, for the built in query 'Pending Security and critical updates', this will mean that no. of machines with security or critical updates pending.
Under Alert logic
Operator - Greater than
Threshold value - You can keep 0. (If Operator = "Greater than", then this will mean that alert will fire when no. of VMs with security or critical updates pending are greater than 0.)
Hope this information is helpful. Do let me know if you have further questions.