// @audit division before multiplication
function _getAvailable(uint256 _tokenId) private view returns (uint256) {
    return getShares[_tokenId] * _getWithdrawablePerShare() - getWithdrawn[_tokenId]; 
}

/// @notice Get the amount that can be withdrawn per share.
function _getWithdrawablePerShare() private view returns (uint256) {
    return (_totalWithdrawn + _asset.balanceOf(address(this))) / getTotalShares;
}
getShares[_tokenId] = 1e8
getWithdrawn[_tokenId] = 0
_totalWithdrawn = 0
_asset.balanceOf(address(this)) = 1e9 (1000 USDC)
getTotalShares = 5e8 + 1
_getWithdrawablePerShare() = 1e9 / (5e8 + 1) = 1
_getAvailable() = 1e8 * 1 - 0 = 1e8 = 100000000
getShares[_tokenId] * _asset.balanceOf(address(this)) / getTotalShares
= 1e8 * 1e9 / (5e8 + 1) = 199999999
