Ok, update your Alert search with by adding | search Result1="Error" OR Result2="Error" and then change the Trigger Condition to number of results greater than 0.
Also, make sure the alert is set Trigger Once, not For Each Result. Let's say you're scheduled the alert for every 5 minutes looking back at the last 5 minutes...with "For Each Result" set, if your search returns 20 events below 40%, you'll get 20 alert messages. If you set to "Trigger Once", you'll get 1 alert if the search returns any events below 40% within the last 5 minutes. This way, at most you'll get 1 alert every 5 minutes, but only if Result1 or Result2 went below 40% once within the last 5 minutes.
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