I can only assume that is exactly what you typed. In which case you have the file name wrong. You are missing the 0 before the 6.

Here’s a tip. In the linux command line the tab key can be very useful. For example if you type the following

tar xf custom

then hit the tab key. It should auto complete to the file name. If there are more than one file name that starts with “custom” you will have to hit it twice to get the list of possibles.