Does your vehicle have a manual transmission? If so, it may have a leaking clutch master cylinder, or the new brake master cylinder was installed incorrectly or is bad. You may also have residual brake fluid trapped somewhere and it is leaking onto the floor.
I have a 95 mazda 626 and I had that same brake fluid leak. I replaced the master cylinder and that didnt help the leak problem. I then replaced the clutch master cylinder. This fixed the internal brake fluid leak but I still had an external fluid leak. Then I replaced the slave cylinder and the leak was fixed.
If you have a manual transmission, it's probably the clutch master cylinder causing the leak inside your car.