Hi Alberto Gugel, thanks for the example! Exactly: when the ticket was created or updated in March, an SLA policy was applied, and its First Reply Time metric was achieved.

Later on, some update between that date and Apr 27 caused an SLA policy change. This is likely because of your SLA conditions; your second policy is probably identical to the first but more specific (applying if the ticket belongs to a specific Organization, for example). So this table doesn't mean that multiple SLA policies are applied to the ticket, it shows the SLA policies that were and are applied to the ticket.

Regarding your last question, I don't quite follow, I'm sorry. Applying a tag is just a simple way to update the ticket without interfering with workflows, and this update will force Zendesk to check all triggers first, then all SLA policies second. Because it's a new tag, triggers shouldn't fire... And if there's a new policy that matches the ticket, it will be applied.