I can't find example for that

[thigrand]

Hey,
Sorry if this is wrong place to ask. But i can't find any answer for that question:
I examine naming-lines and repeat() method connection.
There is this sentense on w3c spec: (https://www.w3.org/TR/css-grid-1/#funcdef-repeat)
"If the repeat() function ends up placing two adjacent to each other, the name lists are merged. For example, repeat(2, [a] 1fr [b]) is equivalent to [a] 1fr [b a] 1fr [b]."
So, how can i use this middle part(line name), or connect to second column by line name? Because everytime i use 'a' line name it reffers to 1st line. When i try tu use 'b a' nothing happen.
So from my perspective equivalent for 'repeat(2, [a] 1fr [b])' is '[a] 1fr [b] 1fr '.
Is this a bug or i can't understand that part?