Subnetting query

[Roady]

Im learning subnetting at the moment and I want to work out my work LAN network structure.
Ill try and keep this simple; one of the ip address's is 19.194.254.75/23. This works out, using the Boolean And method, that the network number is 19.194.254.0, which sounds correct. But using methods that ive used to work out the number of hosts per subnet on other scenarios worked ok.
I worked it out that there are 510 hosts allowed per subnet with 128 subnets, is this correct?
Using the Subnet No. of 19.194.254.0/23 is the below specifications correct?
Subnet ID's supported
19.194.0.0
19.194.2.0
19.194.4.0
19.194.6.0
----------
Last subnet 19.194.252.0

Valid hosts per subnet
19.194.2.1 - 19.194.3.254
19.194.4.1 - 19.194.5.254
19.194.6.1.- 19.194.7.254
---------- -----------
Last valid host
19.194.252.1 - 19.194.255.254

If I have gone wrong how would you work this problem out?

Thanks to all that reply.

G.S.