GST credit note

our company using transport services of xyz pvt.ltd.
xyz wrongly charged 12% GST instead of 5% on invoice. let's say
bill 100
tax amount 12rs (12%)
now we demand him credit note of 7%
he gave us credit note of total RS 7
but gave bill like this
7*12/112
basic amount 5.5
cgst.75
sgst.75
total 7
is this right???
we charged transport GST as expense


when xyz gave us credit note