The total transaction count (for progress estimation) is counted as the known count at the last checkpoint, plus an estimated number per day.

The last checkpoint is now 996 days ago, and its estimated 60000 transactions per day leads to a total estimate of 96M transactions, while the real number is around 183M.

Fix this by updating the count, timestamp, and rate of transactions... with or without adding a new checkpoint.
};
struct SeedSpec6 {
    uint8_t addr[16];
    uint16_t port;
};
typedef std::map<int, uint256> MapCheckpoints;
struct CCheckpointData {
    MapCheckpoints mapCheckpoints;
};
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