The cost basis shown on the Transactions page is calculated according to the selected cost basis method on the Settings page (FIFO by default), and this value might sometimes look wrong even though it isn't.
All of the transactions imported are being considered when Coinpanda calculates the cost basis, but you can easily verify how the cost basis is actually calculated by using the Cost Analysis tool.
For countries like the UK and Canada, cost basis calculations are even more complex by considering both your past and future purchasing history when determining the cost basis. You will therefore need to have a fairly good understanding of how these calculations work and use complex Excel/Google sheets if you want to calculate this manually.
Example - FIFO
You received 0.7 BTC on May 20th and then sold 0.7 BTC on June 15th. The cost basis of BTC sold is calculated as $4,709 while the cost basis of 0.7 BTC received is $6,667. This means that you have older transactions not seen in this screenshot assuming that FIFO is the selected cost basis method.
You can open the detailed transaction modal by clicking anywhere in the transaction row and then Cost Analysis to see the full breakdown of how the cost basis is calculated:
As we can see, the cost basis of $4,709 is calculated from three prior transactions between January and March 2020.