[SnowmanDK]

First, merry christmas, happy hanuka, or whatever

With the great help from all you guys, then I ended with what I think is my final code.
I may no have used what you all suggested, but you still inspired me
function:

local function UpdateBaitAmount()
    if DestinationsSV.filters[PINS_FISHING_SHOW_BAIT_LEFT] then
        local numLures = GetNumFishingLures()
        local oldBaitCount = defaults.data.FoulBaitLeft + defaults.data.FoulSBaitLeft + defaults.data.RiverBaitLeft + defaults.data.RiverSBaitLeft + defaults.data.OceanBaitLeft + defaults.data.OceanSBaitLeft + defaults.data.LakeBaitLeft + defaults.data.LakeSBaitLeft + defaults.data.GeneralBait
        local baitCount = 0
        for lureIndex=1, numLures do
            if stack then
                baitCount = baitCount + stack
            end
        end
        if baitCount ~= oldBaitCount then
            LMP:RefreshPins(PINS_FISHING)
        end
    end
end

call:

ZO_PreHookHandler(ZO_WorldMap, "OnShow", UpdateBaitAmount)

I know I COULD have chosen to just fire the LMP:RefreshPins(PINS_FISHING) every time the map opens to skip the comparison of stacks, but I think this will have a smaller impact on the game.