When a model is first created the first entry in the History is
If Workflow is enabled on a list, any automatic change to workflow triggered by data changes will show up as . Eg. If a list item is set to workflow 'Not Started', any data a user enters into a cell relating to that item will automatically change the status of that item to 'In Progress'. It is this automatic change from 'Not Started' to 'In Progress' that is recorded in the history as a
Automatic updates to the list of users in a model also show as . Eg. When you add/remove a user in a model, this is done at workspace level - so when you open a different model in the workspace it automatically synchs up with the latest list of users. This means in the model where the user was added/deleted the history will show the user who made that change, but in all other models in the workspace as they automatically synched up to show that change they will show as a in the history.