The market value (now) is calculated based on your current cryptocurrency holdings tracked by CoinTracker. The chart's market value is computed based on your historical transaction history. If your complete trading history (e.g. all fiat → crypto → crypto → fiat transactions across all exchanges and wallets) is not tracked by CoinTracker, then these will not be accurate and not match. In order to fix this, please follow these steps.
Note: the chart updates at the end of each day so if you have same-day transactions, the plot may be out of sync from today's transactions. Additionally if you are viewing your performance page on a date other than today (e.g. past or future), then the calculation changes to be based entirely on transaction history like the chart. Therefore if your complete transaction history is not added to CoinTracker, there will be a discrepancy between the values from tabulating your transaction history and your current holdings.