Unless there is something defined under the "Alert Escalation" tab of the alert action itself (such as "Execute this action repeatedly while the alert is still triggered") then these alerts should not be sending you another notification email unless the condition was no longer true and cleared. The easiest way to know if this is occurring is to define a "Reset Action" that sends you an email when the condition is no longer true. I would still recommend reducing the complexity of the alert to see if this too is playing a factor in these alerts re-triggering. The only two lines in your trigger condition that are needed are as follows. The rest are redundant and could have unexpected results.
Trigger Condition (when all apply):
Volume Type is equal to Fixed Disk
Volume Percentage Used is greater than 95
