Need info on my grand daughter's EOS Rebel T7 lens dimensions

[showme]

My teen granddaughter recently got a Canon EOS T7 Rebel with an EF518 55mm. She's volunteered to be a photographer for the school newspaper, so my wife and I wanted to get her some lens equipment for Christmas. My wife handled the search and purchase of a lens set that she found on amazon that stated they fit the T7, along with a list of others.

It seems that my granddaughter's camera's lens base is smaller than the one's we ordered. They are 58mm, and as far as I can see, when I measured her camera (she didn't have the manual with her, and wasn't sure where to find the base measurement on her camera), I found it is 50-51mm in diameter, depending if I used the inside diameter (50mm) or estimated the thread depth diameter (51-?). So, after doing a little research, I see there are 50mm lenses, but I'm a little mixed up here, since the box that her camera came in states the zoom lens is 55mm(??). 

What does this 55mm dimension indicate, the lens diameter or the base diameter? And, would her camera's lens base be considered 50mm or 55mm? I really can't see another 5mm of thread depth on top of the 50mm inside diameter of the camera's female lens base receptacle. So, as a no-nothing grandfather of a future photography nut, I'm asking all the experts here (i.e., anyone who knows more than me about these things) for help to figure out exactly what we need to get her. Btw, I realize we could wait until Christmas break is over and have her ask her instructor about it, but she was so disappointed when she found out she wouldn't be able to use it this week, I wanted to find one that fits her camera asap. This is what my wife ordered, and is now being returned. Their bases were too big to screw into the camera.

Thanks for any and all comments and suggestions on this. I appreciate it. Lee

[Commercial link removed per community guidelines and replaced with screenshot to serve as a visual aid.]

[showme]

Thank you, Tronhard! That's great, and I will pass this on to Kate. 

[showme]

I found the page from Canon's site that includes the manual on the lens, along with a truck load of other information for her to peruse. What a gold mine of information! I should have looked before I asked, but you all have given such good information, I think this is a great place to start.

[kvbarkley]

But this person has never shot with a full frame camera. Why should they care about equivalence?

[shadowsports]

kvbarkley is correct.  The crop factor applies based on the sensor size. The FL does not change.  The OP is using a APS-C sensor, so my previous statement does not apply.  kvbarkley, thanks for pointing his out.    

[rs-eos]

It's useful to know if wanting to pick up new lenses based upon seeing what others are capturing.

e.g. an owner of a crop-sensor camera may see an image online of a landscape tagged with 14mm and camera used being full frame.  The owner likes how much of the scene can be captured, so picks up a 14mm lens.  But is now disappointed that it's not as wide (since FOV equiv is 22mm).   So if they know about the crop-factor, they'd then know to get a lens around a 9mm focal length.

[Tronhard]

It was a response to your post , which was itself a response to shadowsports, for your attention