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- There is no limit on how many filters can be added - but of course creating too many of them is not recommended as it can be hard to manage them.
- Some of the fields in JIRA or TFS / VisualStudio Team Services are truly array of values - like Labels for example. Operator chosen in filter is checked against each of the value in this array separately, so for example if filter has 'contains' operator then it's checked if at least one label in given issue contains text specified in the filter.
- Filters are case insensitive.
- Filtered field doesn't have to be mapped in Field Mapping.
- When there are no filters specified for JIRA and TFS / VSTS then all of the issues / work items are synchronized.