File: contracts/utilities/poolsUtility/Position.sol
322: function _calculateDebt(
323:         address _bathToken,
324:         uint256 _startBlock,
325:         uint256 _borrowedAmount
326:     ) internal view returns (uint256 _debt) {
327:         uint256 _blockDelta = block.number - _startBlock;
328: 
329:         uint256 _interest = (
330:             (_borrowedAmount).mul(borrowRate(_bathToken).mul(_blockDelta))
331:         ).div(10 ** 18);
332:         _debt = _borrowedAmount.add(_interest);
333:     }
each transaction on L2 is placed in a separate block and blocks are NOT produced at a constant rate
cast block-number --rpc-url YOUR_OPTIMISM_RPC_URL
