Exceed oasis city limits

hiii,

Can anyone help in the game play.
i have won a attack against one owner.
after winning the attack, the mail reads that exceeds oasis limit.
Please help me what does it mean.

[Kad601]

You have attacked and won a battle against an enemy oasis. This can be a crop field, forest (lumber), mountain (stone), or mine (iron). Upon winning you will capture the targeted oasis if you have a free oasis slot. The total number of oases a player may hold is equivalent to level/2 rounded. So if you are level 4 you can hold 2 oases and at level 5 you can have a 3rd. The mail you received is simply an indication that you currently have too many oases to capture a new one. You can either resign one oasis from the cities tab or wait until you lose one of your own oases either by being captured or more likely time. Oases lose levels over time. When an oasis hits level 0 it will automatically be forfeit and begin regenerating.

Hope this helps Haypi hunting!