The short answer
Credits are how your usage is billed in Dlubal CALC. You choose the reasoning tier with the gauge icon below the chat input. A chat message on Standard costs 1 credit, and one on High costs 2 credits. The price stays the same regardless of message length, chat history, or attachment size. Additional actions, such as RFEM modifications or PDF reports, have the charges shown in the pricing overview. What a task costs in total depends on how many messages and actions it takes. Each of them has a fixed credit price. Your balance is shown in the sidebar, and the Usage page lists what you have used. If Mia delivers no answer, for example because of a connection error, the credits for that message are returned automatically.