Using a Bitcoin-Qt v0.16.0 ([downloaded from bitcoin page](https://bitcoin.org/bin/bitcoin-core-0.16.0/bitcoin-0.16.0-osx.dmg)) in an macOS High Sierra 10.13.4 

When I start after a fresh install Bitcoin-Qt as a mainnet node and wallet, the wallet prompt that about 203gb is going to be used in my disk
![image](https://user-images.githubusercontent.com/20187136/39899688-ba820bfe-5493-11e8-87d9-460ed5716a02.png)

When I start the node and wallet as testnet, shows the same message about the 203gb disk usage
![image](https://user-images.githubusercontent.com/20187136/39899756-17b31214-5494-11e8-8a57-60e604e74afb.png)

It seems that the second time the message is wrong, due that the testnet database uses about 14gb.
/**
 * Holds various statistics on transactions within a chain. Used to estimate
 * verification progress during chain sync.
 *
 * See also: CChainParams::TxData, GuessVerificationProgress.
 */
struct ChainTxData {
    int64_t nTime;    
    int64_t nTxCount; 
    double dTxRate;   
};
/**
 * CChainParams defines various tweakable parameters of a given instance of the
 * Bitcoin system. There are three: the main network on which people trade goods
 * and services, the public test network which gets reset from time to time and
 * a regression test mode which is intended for private networks only. It has
 * minimal difficulty to ensure that blocks can be found instantly.
 */
class CChainParams
{
public:
    enum Base58Type {
        PUBKEY_ADDRESS,
        SCRIPT_ADDRESS,
        SECRET_KEY,
        EXT_PUBLIC_KEY,
        EXT_SECRET_KEY,
        MAX_BASE58_TYPES
    };
    const Consensus::Params& GetConsensus() const { return consensus; }