TFS 1.X+ NPC exchange storage points to premium points.

[OTcreator]

Hi,
I am trying to make an NPC that converts mission points into premium points, with 5 mission points being 1 premium point.
I tried to do it this way:

local player = Player(cid)
local tstorage = 8005
local task = player:getStorageValue(tstorage)
local exchange = (task / 5)

local function doPlayerAddPremiumPoints(cid, count)
   db.query('UPDATE accounts SET premium_points = premium_points+'.. count ..' WHERE id = ' .. getAccountNumberByPlayerName(getCreatureName(cid)))
end

if task >= 5 then
    -- how do it when player have 103 points (= 20 premium points and 3 stay on storage?)
    player:setStorageValue(tstorage, (task - (exchange * 5)))
     doPlayerAddPremiumPoints(cid, exchange)

I have an error in the console related to just sending information to the database....