When boolean is selected as a line item format, there should be an option to have single or multiple selections allowed. Currently, the default is to allow multiple selections. For instance, for single-selection, once one line item has been checked, all of the other line items have a greyed out checkbox that cannot be changed unless the original checkbox has been unchecked.
The content in this article has not been evaluated for all Anaplan implementations and may not be recommended for your specific situation.
Please consult your internal administrators prior to applying any of the ideas or steps in this article.