cloudstep makes many calculations in order to generate a reliable financial model. Every time a change is made or a new element is added any Elements related to that change must be recalculated.
This process takes time and in order to allow you to continue to use the application making more changes a background worker goes along and tends your financial model making changes as needed. Think of it as a robotic accounts person that hoovers up your changes and puts them in a giant ledger.
cloudstep might make lots of changes when you change one little thing. For instance if you change your policy for AWS EC2 instances to be only on-demand pricing then every EC2 instance in the model will need to be recalculated. This happens in order and when each one is finished cloudstep will tell you through its notification system.
You'll see several notifications appear in the bottom left hand corner of the screen explaining what's been updated. These will automatically disappear after a few seconds. To see the history of the last few hours of messages you can click on the Message menu (the little flag) in the top navigation to see the history. The flag will show how many messages are there to be looked at. You can ignore them or you can delete them by clicking the x next to the message.