meaning of term...

Lemme try to interpret it & explain in hindi

Mana jayega (i.e. presume kara jayga) ki agreement writing mein hai,
but agar koi proof ho samne jisse ki ye sabit hojaye ki agreement writing mein nahi tha, sirf tab hi mana jayega ki haan sach mein agreement writing mein nahi tha.

In short, agar proove kar do ki written mein agreement nahi hua tab he usko non-written agreement kahenge, warna presume toh kiya hua hai ki wo written hai. "WRITTEN" is the presumption..

I hope I made it clear.. 😊

thanks a lot....