cloudstep.io can be thought of as a giant spreadsheet where each of the rows represents a model Element and each of the columns represents a month in the modelling period (often 5 years or 60 months). In the same way that a spreadsheet needs to recalculate when you make a change, cloudstep.io needs to do the same.
It depends on the Element and what has changed. In general though, descriptive fields about an Element don't trigger reclculation. Its only when we change something that would alter how we consider costs that we reclculate. The following is a list of what triggers recalculation:
|Start or Stop Date||Application, Implementation, Infrastructure, Project||
|Dependencies||Application, Implementation, Infrastructure||
Cost recalculation happens "out of band" meaning that a job is farmed off to recalculate the model for you. This means you won't see the change immediately, it can sometimes take a few minutes. To understand this more see the documentation on Eventual Consistency.