it's when you take the bimini in two separate arches, without closing the rear one onto the front one. In this picture you can see the rear stell arch with the rear bimini part rolled on it and the front arch with the bimini open.
To roll the rear fabric around its rear arch you have to close it in that small rectangular part you are asking about. It's only the outside "envelop" with zip for closing.
Yes sometime it's hard for me explaining since english is not my mother language I apologize for this.

for the speedo i really don't know but it can be as well that the small pipe leaks water, surely the check of the pump needs only few seconds. try with it as well.
Oscar