Read following links and improve the addon.

• https://www.wowhead.com/guide=1949/addon-writing-guide-a-basic-introduction-by-example
• https://wowprogramming.com/

Expected features:

• Show(Alert?) the buff remaining second(not debuff) on startup
• Show the message in message box
• Do not show the message if buff has no time limit

UnitAura api:
https://wowprogramming.com/docs/api/UnitAura.html

Ref Macro Options:
https://wowwiki.fandom.com/wiki/API_UnitAura