Latest Items from individual categories- home page

[Horizon]

The default recently added content block has the code:

Only registered members can view the code.

I want to show the newest 4 ads from the category with ID 623, so I created a new content box as follows:

type: php

Only registered members can view the code.

but it doesn't limit it to the category with id 623, it still shows recent listings from all categories.

Is there something else I should enter in this block to make it show the recent listings only from category 623?
Or do I have to still do a code modification to make this work as in earlier years?