[Ayantir]

Something like this adapted to your code :

function ZO_HUDTelvarMeter:UpdateMultiplier()
    
    local baseMultiplier = GetTelvarStoneMultiplier(self.telvarStoneThreshold)
    local realMultiplier
    
    if GetCurrentMapIndex() then -- Sewers returns nil
        realMultiplier = baseMultiplier + (self.actualDistrictBonus / 100) * baseMultiplier
    else
        realMultiplier = baseMultiplier
    end
    
    local wholePart = zo_floor(realMultiplier)
    local fractionalPart = zo_round(zo_mod(realMultiplier, 1.0)*100)
    HUD_TELVAR_METER.multiplierWholePart:SetText(zo_strformat(SI_TELVAR_HUD_MULTIPLIER_VALUE_WHOLE, wholePart))
    HUD_TELVAR_METER.multiplierFractionalPart:SetText(zo_strformat(SI_TELVAR_HUD_MULTIPLIER_VALUE_FRACTION, string.format("%02d", fractionalPart)))
 
    
end
 
local function OnPlayerActivated()
 
    if IsInImperialCity() then
        
        self.actualDistrictBonus = 0
        for keepId in pairs(ICKeeps) do
            local owningAlliance = GetKeepAlliance(keepId, BGQUERY_LOCAL)
            if owningAlliance == self.playerAlliance then
                self.actualDistrictBonus = self.actualDistrictBonus + GetDistrictOwnershipTelVarBonusPercent(keepId, BGQUERY_LOCAL)
            end
            ICKeeps[keepId] = owningAlliance
        end
        
        self:UpdateMultiplier()
    
    end
 
end
 
local function OnObjectiveControlState(_, objectiveKeepId, _, _, _, _, objectiveControlEvent, _, objectiveParam1)
    
    if IsInImperialCity() then
        if objectiveControlEvent == OBJECTIVE_CONTROL_EVENT_CAPTURED or objectiveControlEvent == OBJECTIVE_CONTROL_EVENT_RECAPTURED then
            if objectiveParam1 == self.playerAlliance then
                self.actualDistrictBonus = self.actualDistrictBonus + GetDistrictOwnershipTelVarBonusPercent(objectiveKeepId, BGQUERY_LOCAL)
            elseif ICKeeps[objectiveKeepId] == playerAlliance then
                self.actualDistrictBonus = self.actualDistrictBonus - GetDistrictOwnershipTelVarBonusPercent(objectiveKeepId, BGQUERY_LOCAL)
            end
            
            ICKeeps[objectiveKeepId] = objectiveParam1
            self:UpdateMultiplier()
            
        end
    end
    
end
 
 
ZO_HUDTelvarMeter:Initialize(control)
 
    self.actualDistrictBonus = 0
    self.playerAlliance = GetUnitAlliance("player")
    self.ICKeeps = {
        [141] = true,
        [142] = true,
        [143] = true,
        [146] = true,
        [147] = true,
        [148] = true,
    }
    
    control:RegisterForEvent(EVENT_PLAYER_ACTIVATED, OnPlayerActivated)
    control:RegisterForEvent(EVENT_OBJECTIVE_CONTROL_STATE, OnObjectiveControlState)
     
    ...