Cheque has been given as security before land purchase

I purchased a land for amount 20L with area mentioned as 1230sq.ft in original land document whereas in government patta the area is mentioned as 1170sq.ft, a mismatch of 70sq.ft. Before land registration, I asked the (then) land owner about this, they told us whatever mentioned in land document is correct and numbers in patta might be wrong. I was unable to confirm this before registration, so during registration I gave 19L cash and cheque for 1L with future date(as security deposit, we had oral conversation stating that if this 70sq.ft is confirmed, I'll give 1L cash and they need to return my cheque). After few days with help of land surveyor, I can able to confirm that this land has only 1170sq.ft which is mentioned in patta. After 2months of land registration, the then(old) land owners demanding those 1L and it looks like they're threatening us, having my cheque in hand. I've cancelled that cheque 1month before with help of bank. Need your suggestions, to proceed legally.