Tailgate/Camping

I have a Slimeline dish for the house. I purchased a 18" round dish (not completely round it is oval but only has one LNB) to tailgate with. I cannot get the receiver (D12-300) to save the 18 inch dish settings. Everytime I try to do the signal strength test it tells me i have a tilt of 71 degrees.

Thank you for any and all help!

Steve