I do not recognize that number, though eBay did at one time have a similar number -- the last four digits correspond to "eBay" on a phone keypad. That does not necessarily mean the phone number is actually eBay or is not eBay. Typically eBay requires users to request a call back rather than telling folks to call a number, but there may be phone number somewhere for security issues or for users having trouble signing in.
eBay does send messages about sign in activity, though I have not seen such a message with a phone number attached. Typically the message includes details of the sign in -- time, location and browser version, with a note that if the sign in activity does not correspond to your own activity, then you should consider changing your password and examining your account details closely.
eBay has begun sending such messages for each sign-in from an unrecognized browser. Unrecognized just means that the browser has no cookies from a previous sign-in to that account, or the IP address does not correspond to a previous sign-in.
If you are routinely erasing your browser cookies, or changing your network address, you can expect to receive such messages when you sign in again.
Do the browser, location and time correspond to your own sign-in activity? If so, you can ignore the typical message that appears in your eBay messages or as an email.
Your message sounds like it appears when trying to sign in and actually is preventing you from signing in. If that is the case and you are unable to sign in using another device or method, you may need to call that number -- but I would be hesitant to provide any private account details unless whoever answers can prove that they are actually connected to eBay and not some random scammer that managed to hijack your browser.
