Event emitter listener jump tokens


We are writing sample NFT contract with use OpenZeppelin. But We wanted try event Transfer inside the _mint function of ERC721 standard before deploy. We writed sample script with etherjs, ABI and contract address. We are listening event stream like this;

contract.on('Transfer', (from, to, value) => {
        console.log(from, to, parseInt(value._hex,16))

But, We noticed tokenId (so value param) jump without arithmetic increment as 1030, 1031, ..., 1067, 1068.

We want to listen this event stream as correctly way.
How to do this?

Thank you for interest.
Good works.