you extend the width of the parent element.

yes slate is right, you can easily see this with the following commands
vgui_drawtree 1
vgui_drawtree_draw_selected 1
and if you keep opening with the +sign on the new window, you will find the hud elements and see the hud player health wide value is limiting the positions u can move the health cross
i see many questions here regarding this shit, and myself included had no idea i could do that till a few weeks ago.
A video tutorial of this would be really helpful but if you follow this stuff you´ll figure it out easily.

Can someone give a more detailed explanation? I changed the wide value in HudPlayerHealth and nothing happened.

Try editing the parent element in hudlayout.res to make it wider; that should do it. Hudplayerhealth.res has been in my experience rather annoying to edit as there are a lot of moving parts, so it is possible you're doing something else wrong too. Let us know if you have further difficulties.

because changing the wide value doesn´t necessarily mean that will increase the wide value to the left of the element, it might have just changed its width to the right still clipping our health cross

Move the actual element within hudlayout.res to the left, and move the health image and health values to the right within HudPlayerHealth.res