I did some test about this.... The problem is how the game is counting the stages ( I guess ), because I noted, doing ALL separated stages (engines and decouplers) still having the same issue. Changing them to the same stage, sometimes fixed it, but sometimes it calculate worst hahaha, let me explain it: I was about to launch, and I decided to check this first... and I noted: Before start Stages, the "Stage Only", only showing the Batteries, its ok... Cutting all the power and activating the stage, it will start to show the Fuel in that stage, but sometimes, for any reason it is adding the LAST stage fuel!!! why? its a mistery!! BUT.... in the VAB... do click in the decoupler and release all in the air (not connected to the vessel), then click it again and adding it... doing this with all decouplers. In some cases, the "Stage Only" showing it correctly... strange. Also, i tested, the stages fuel calculation have troubles if you add a part in the fuel tank... Its like that will turn that Fuel tank always in the calculation (I tested it just with solar panels), with they into that stage, it add the fuel to the calculation, moving the solar panels to the cockpit, it will not... strange hahahahaha. Are there a Kerbalien into my ship? And, i must say, this "Stage Only" feature its really useful in MAP view, overall if you create several stages for long flights and you must burn a lot of fuel. Yes... its true... the funniest view is Flight mode, but if you see for eficiency... you NEED this hehe. Best regards guys!