Is 6-ethenyl-4-(prop-2'-enyl) octa-6-en-3-ol a valid name? I recently study organic chemistry and I read a book by Sana Jamshaid. I came across this compound and I cannot understand why it named 6-ethenyl-4-(prop-2'-enyl) octa-6-en-3-ol:



I understand that the longest chain is 8, hence octa (but if we go up on the 4th longest can be 9) but I don't understand the 4-(prop-2’-enyl). Are there any explanations to why the compound named in such way? The double bond also sits on the 7th and not the 6th.
The suggested name
“6-ethenyl-4-(prop-2'-enyl) octa-6-en-3-ol”
is not correct; the closest valid name is
6-ethenyl-4-(prop-2-en-1-yl)oct-6-en-3-ol.
However, this name does not describe the compound that is shown in the picture. Note that the parent chain actually is non-7-en-3-ol instead of oct-6-en-3-ol, and the longest side chain actually is but-3-en-1-yl instead of prop-2-en-1-yl.
Therefore, the correct name for the compound that is shown in the picture is
(7E)-4-(but-3-en-1-yl)-6-ethenylnon-7-en-3-ol.