Progress with tasks which are already done?

[Bia10]

So lets say I want to use progress like this.

            AnsiConsole.Progress()
                .AutoRefresh(false) // Turn off auto refresh
                .AutoClear(false)   // Do not remove the task list when done
                .HideCompleted(false) // Hide tasks as they are completed
                .Start(ctx =>
                {
                    var task1 = ctx.AddTask("[green]Parsing facWalk files:[/]",true, facWalkFiles.Count);
                    var task2 = ctx.AddTask("[green]Parsing mes files:[/]", true, mesFiles.Count);
                    var task3 = ctx.AddTask("[green]Parsing sector files:[/]",true, secFiles.Count);

                    while (!ctx.IsFinished)
                    {
                        foreach (var file in facWalkFiles)
                        {
                            ParseAndWriteFile(file, FileType.FacadeWalk, dirPath + @"\out\");
                            task1.Increment(_facadeWalksRed);
                        }
                        foreach (var file in mesFiles)
                        {
                            ParseAndWriteFile(file, FileType.Message, dirPath + @"\out\");
                            task2.Increment(_messagesRed);
                        }
                        foreach (var file in secFiles)
                        {
                            ParseAndWriteFile(file, FileType.Sector, dirPath + @"\out\");
                            task3.Increment(_sectorsRed);
                        }
                    }
                });

Any of the files.Count may be 0 which should imply that the task is done and no calculation of percentage is needed,
however it claims that percentage is NaN which implies 0.0/0.0, why is there need to calculate percentage on tasks which are done already? Can there exist a task which is done and yet its percentage is different from 100%?