If your question is why same TQ fare for trains via GNT and via BZA to SC from OGL, then Minimum Distance for charge for Tatkal (in Km) is 500 for SL, 3A and 2A. Whereas it's 100 for 2S and 250 for CC and Executive Class.
12603 from OGL to SC is 414km {for 12603, BTTR to SC fare for tatkal is 415/- and distance is 496km}
12759 from OGL to SC is 487km