Malitol is a sugar alcohol. They either go right through you (in which case they can cause gas and rushing to the loo if you eat too much), or they are absorbed very slowly so they don't do much damage.

Some people say sugar alcohols make them stall. Others are OK with them. I have them as a treat from time to time.

'Too much' sugar alcohol is more than about 25g at one go for most people. Your bar with 13g is OK - but don't eat two or three of them at one sitting!