Confused about address of 2nd, 3rd, 4th, etc subnet

I'm having trouble figuring out which network address I would use if I created X amount of subnets and I want the address for the 2nd subnet or the 5th subnet or the 7th. I'll make an example to show the way I'm doing it:

Address 192.128.128.128 /25 where I want to borrow say 6 network bits to create 60 hosts making the new subnet mask /31.

The first 25 bits are part of the network, the last 32nd bit is a host, bits 26-31 are part of my subnets. If I want the 5th subnet from this, then should those 5 subnet bits in binary be 00101 which equals 5 or should they be 5-1 which equals 00100? Basically, is the first subnet here 00000 making the first network address 192.168.128.128 or is the first subnet 00001 making the first network address 192.168.128.130?