That's right, it's only one tph each way more than usual since the Clitheroe to Manchester service would have operated Blackburn to Manchester anyway, it's only the Blackburn to Clitheroe extension which is different. This has been the recent routine if the line via Darwen has been closed, i.e. the remaining Blackburn to Clitheroe section has been 'tagged' onto the Manchester to Blackburn via Todmorden.