Understanding Index Performance using LIKE Keyword

I am using the AdventureWorks2017 database from Microsoft.

I have done the following:

create index idx_CarrierTrackingNumber on [Sales].[SalesOrderDetail] (CarrierTrackingNumber);
go
--------------------------------------------------------------------------------

select 
    CarrierTrackingNumber
from
    [Sales].[SalesOrderDetail]
where
    CarrierTrackingNumber like '%4';
go

When I go to look at the Execution plan, it shows the following:

Index Still Used despite LIKE operator

Shouldn't a table scan be used instead of an index scan because the first character in my LIKE search is a wildcard?

Edit #1: Added why I believe this

I was reading a book, SQL Performance explained and in the book, it says:

The opposite case is also possible: a LIKE expression that starts with a wildcard. Such a LIKE expression cannot serve as an access predicate. The database has to scan the entire table if there are no other conditions that provide access predicates.

Did I misunderstand what the author is talking about?