RC-Pier Footing Output

In the output for LRFD footing design, under the Cracking/Fatigue section, there are "Srqt", "Srqb", "Sprt" and "Sprb" heading with the unit of 'inch'.  I cannot find anything in the manual or help that identifies what these heading are for.  Can anyone help me out with the nomenclature?  TIA.