Depends on the station and route. On my usual route to/from Accra, they ALWAYS enforce not only the one piece rule (excluding Duty Free bags which are allowed without restriction ) but also the 7kg limit. I've had to remove my laptop charger and some papers from my backpack on occasion to squeeze under the limit. 7.1kg was not acceptable to them. Business Class is allowed 2 pieces, but the 7kg limit is applied strictly there too. Elsewhere in the system, they are a lot less strict.