Add this code to the Custom CSS field on the Appearance tab of your LinkedIn Feed widget’s settings:
.es-grid-layout > *:nth-child(n+10){
display: none;
}
In :nth-child(n+10), you should replace 10 with the post number up to which you want to show posts, adding 1 to the number you want (for instance, to display 9 posts, use 10):
:nth-child(n+10) = will show 9 posts
:nth-child(n+5) = will show 4 posts