Use the Number Sequences dialog to adjust rebar numbering sequences.
To open the dialog, select a rebar, go to the properties palette and click the "#" button next to Rebar Number. In the Numbering Template dialog, click Edit to open the Number Sequences dialog for that template
Alternatively, go to the Manage tab > Settings panel > Numbering. In the Numbering Options dialog, select the template you want to edit (e.g., Rebar Numbering) and click the Number Sequence button.
By default, numbering templates for Rebar, Fabric Sheets and Couplers are set-up to use the Partition parameter to define numbering partitions. You can set the value of the parameter for all elements in the same partition in the Numbering Sequences dialog. See Partitioning and Numbering Sequences