[Learn]: Question confusing

[martipello]

Step Number: 32
Step Name: steps.groupReference.title
Language: en
Version: v2.30.0

User Agent:
Mozilla/5.0 (Macintosh, Intel Mac OS X 10.15, rv:130.0) Gecko/20100101 Firefox/130.0

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What is the problem you are experiencing?

i found this one confusing i think because it doesnt explain that here
(ha)-\1,(haa)-\2
the (ha) is considered part of the group and the - is outside it, this isnt explained