The effect of a counter-offer is that it destroys the offer and replaces it with its own offer
If you offer to sell me your car for £2,000 and I say ‘No, but I’ll pay you £1,800’ my £1,800 counter-offer destroys your £2,000 offer
You turn back to me and say ‘No’
‘OK’ says I. ‘I’ll accept your offer to sell for £2,000’
But I can’t! That offer from you of £2,000 to sell your car was destroyed by my counter-offer
And you are now in the happy position of being able to accept my new offer of £2,000 or telling me to go fly a kite because there’s no way on this Earth that you will sell me your car!