I've used Inventor and Fusion360 for small personal projects since 2014. In an instance like this, I would just draw a quick 2d shape off of the front face in your picture and cut it. Sometimes it's just not worth the time to figure out. Are you modeling professionally?
If you open up Extrude 8 they have defined the areas of the sketch that are extruded by selecting the areas they want to extrude under "Profiles". Looks like changing dimensions causes it to lose the reference and it needs to be re-selected.
Other than that, your ribs look like they aren't linked to another dimension and when you changed the size of the area they are now broken because they are too short.
But for real thanks! I'll take a look when I sit back down at my windows computer. As far as I know, I didn't change any of the dimensions that would have affected the fins like that... Maybe I changed the wrong parameter.
There were some errors that popped up and then went away. How does one find the timeline? I can also open the original file fresh and make my param changes again.
The timeline should be at the bottom of the editor window, if you're in the default design workspace. If you started in the mesh editor workspace then "design history" might be turned off, in which case you wouldn't have a timeline. It looks like this:
If some of the icons are highlighted in yellow, those have errors, so, things like broken projection links, or missing objects for some operations. You can usually fix those and patch things up.
Edit: oh, sorry, just realized you were working from someone else's file. That might not have design history turned on. The person who told you how to edit the extrusion operation has the right idea.