Enthalpy recovery of a single polystyrene thin film is quantified by both experiments using Flash DSC and modeling using a new modified TNM model. Experimental data include Kovacs' three signatures of structural recovery: intrinsic isotherms after temperature down jumps, the asymmetry of approach after temperature down and up jumps of the same size, and the memory effect after a two-step history. A new modified TNM model is proposed to quantitatively fit all three signatures of structural recovery with a single set of model parameters. Here, we elucidate the detailed derivation of the new modified model and demonstrate its applicability to the experimental Flash DSC results.