To see an overview of your credit spending click on the main menu icon (top right corner), then click "My Account".
There are 3 types of "credit".
Land Registry Credit
Buy Land Registry title plan and title register documents for £3 each. This is your balance in British pounds. You can check exactly which documents you've purchased by clicking on the "Credit Spending" link (on the left) under "My Account".
Monthly Ownership Views
Land Insight provides ownership information as part of your subscription (normally charged at £3 by the Land Registry). This shows the number of times you can click land or property to see who owns the land.
Monthly MasterMap Views
The "OS Maps" (or MasterMap) button allows you to switch to the highly accurate street map. Your account includes a limited number of times you can view the map. You can see your remaining credits when you explore the map - look at the bottom left hand panel.