i was asking the port locals to see if my max player treasure was at it's max and i got this message:

You asked the port locals spending 5 turns.
Your port maximum treasure has been increased by -39,725,000

why should this decrease my max treasure?? i understand the player with the max treasure must've taken out some gc, but why was i charged turns to decrease it? if i didn't update it and spend 5 turns, it would've been 40m larger. this doesn't seem right to use my turns to decrease it

The port locals tend to be honest.

Which means that the treasure has been found or retrieved from that port.