Cutoff frequencies of active this filter?
The passband seem to be between 3.1Hz to 78.1Hz




C4 and R6 define the LF cut-off and that equals 3.38 Hz

C3 and R4 define the HF cut-off and that equals 72.34 Hz

If you are measuring a difference in your sim then this is likely due to imperfections in the LM324 i.e. non-infinite input resistance. There will also be a slight effect due to C6 and R10.