Fuel Tank Vent Tube

Did all the fuel pump mods on my 2010FE 570 and went out on my first ride this past weekend. Worked Great. Stopped to take a rest in the middle of a long ride and decided to check my fuel. Opened the cap and fuel game gushing/FLYING out like a geyser. Very dangerous situation with a hot bike and fuel all over me and the bike. Anyway, after I calmed down and got to thinking about the issue, there is no way the tank should have that kind of pressure in it. Looked at the cap and the inline valve on the breather tube and the arrow on the valve was pointing down. I have never messed with this and have owned the bike since new (did have it in the shop recently though). This valve was set to let air in the tank but not out. I turned it around so that the arrow was pointing up and it seemed to let pressure out just fine. Looking on some of the other forum's here, do I read that this valve is supposed to let air in and NOT out???? Doesn't make sense to me. Does anyone here have a thought on this?

Thank you Ruger.