Inner join returns duplicate results
As far as you don't give us more information I'll throw a bet.

Using only uid to join both tables you get 20 records (5 x 4). I suppose you should add symbol.

SELECT     a.symbol, 
           a.order_type, 
           a.price_open, 
           a.time_open, 
           a.size, 
           b.bid, 
           b.point
FROM       trade_log a
INNER JOIN currency_rates b 
ON         a.uid = b.uid
AND        left(a.symbol, 6) = b.symbol
WHERE      a.uid = '23' 
AND        a.status = 'Open' 
AND        a.order_type IN ('0', '1')
ORDER BY   a.time_open ASC;