Not really the kind of example I was asking for since I can not see your page source.
I gave you two live examples. Here is how we do it in pp-inc.php
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Basically it is all done by css and that right arrow is all relative like I said we can only estimate as the right arrow position would change for every photo. The left arrow is easy as it has no largin it is always to the left and its margin if any is the actual size of the image which is 20px wide. Since we need to show that right arrow by making the margin left a certain size. A fixed number like take 40 pixels off the width does not work as picture sizes change.
I use .93 of the width as that works for most all picture sizes I tested. It may not be exact but it is close.
You can experiment by changing that to .91 or .87 which is what we use in the mobile setup as that was the closest number percentage that works for mobile sizes.