Netplan static IP subnets - am I accidentally adding extra IPs?

I'm not sure if this is the right place to ask this so sorry if not. I've configured a machine running ubuntu server on my network to have two local static IPs like so:

network:
  ethernets:
    enp0s3:
      addresses:
      - 192.168.1.155/24
      - 192.168.1.156/24
      gateway4: 192.168.1.1
      nameservers:
        addresses:
        - 1.1.1.1
        - 1.0.0.1
  version: 2

With this I can ping my machine with both 192.168.1.155 and 192.168.1.156.

Now I'm new to networking but I know that the a /24 mask means all the addresses in the 192.168.1 range, but what does it mean in the case of netplan when I'm supposed to be giving specific IP addresses? Am I allocating more IPs by accident? What would happen if I changed it to /32? Thanks.

In the case of netplan's address configuration entry, /24 indicates the netmask of the network the specified address belongs to, and hence the range of addresses which are directly reachable through that interface.

  addresses:
  - 192.168.1.155/24

means: "Assign the interface the IPv4 address 192.168.1.155 and the netmask /24." So if you later do a ping 192.168.1.234 the OS will know that the destination address is on the same network and try to locate it via ARP (in the case of Ethernet).

  addresses:
  - 192.168.1.155/24
  - 192.168.1.156/24

will assign two addresses within the same subnet, setting the netmask to /24 both times, somewhat redundantly.

If you changed it to /32 then the netmask of the interface would be set to /32 instead, meaning that no other addresses except those of the interface itself are directly reachable through it. So ping 192.168.1.234 would look for a suitable next hop in the routing table, probably hitting the default gateway. If the default gateway is itself in the 192.168.1.0/24 network then it will not be reachable either, so a routing error will occur.