How can I make a procedural grid rectangle

I’m using the ‘create grid mesh welded’ node to create a landscape. I want this landscape to be a narrow rectangle, sort of like a hallway

The ‘create grid mesh welded’ node has 3 inputs: num x, num y, and Grid spacing.

When num X and num Y are 20 - . - Album on Imgur

When num X is 40 and num Y is 20 - . - Album on Imgur

I want to have the rectangle the same as a square just longer on the x-axis. but when I increase num x the y axis gets more narrow and of center.

How can I stop this?