Check the FAQ in Pandora about this problem:
Receiving mails when an alert is triggeredIf your problem persists, please provide us a more detailed information, so we can diagnose it and answer faster.
Feel free to attach screenshots with your configuration as well, as long as you remove all the sensitive and personal information you don't want show.
About your second question, currently there's no way to modify the server uptime in Pandora using the web interface (it's an interesting feature request and we'll consider adding this option in the next version)
Meanwhile, you can create a module in your pandora_agent.conf (located in the servers where you want to get the uptime) with the following syntax:
module_begin
module_name Server Uptime
module_type generic_data_string
module_exec uptime| cut -f 5 -d ' ' | tr -d ','
module_description Server uptime in hours and minutes (hh:mm)
module_end
Regards.