Why do I see infinite symbols as my slack value in PlanAhead?
The infinite symbol is shown on TIG constraints in PlanAhead. This is expected and desired behavior. When a TIG constraint is applied to a path, the slack on that path is truly infinite.
In a timing report, TIG constraints do not show "Slack", but report "Delay". This is because "Slack" is considered for timing violations; whereas, "Delay" is used to make several assumptions about the design and perform a calculation on a false path so that the report can at least display the paths information.