Cast off 7 sts. at the beg. of the next 6 rows, then cast off 8 sts. at the beg. of the next 2 rows. Cast of remaining sts. for the back neck.
Currently I have 92 sts on the needle. If I cast off 7 sts in the next 6 rows that means altogether 84 sts are casted off. Leaving only 8 sts left. Then how can I cast off 8 sts on the next two rows?
From your statement here, You think you should cast off 7 at the begining and the end. That would be the only way you would get 84 stitches casted off in 6 rows. When you start a knit row..(assuming that you are starting your decreasing on a knit row.) You would....
Cast off 7, Knit to the end of the row, turn. (Row 1 of 6)
Cast off 7, Purl to the end of the row, turn. (Row 2 of 6)
Repeat till you have done 6 rows, 3 knit, 3 purl rows.
That will give you a cast off of 42 stitches.
Then It instructs you to cast off 8 stitches at the begining of the next 2 rows. (by my calculations, you should be ready for a knit row here) This would be......
casting off 8 stitches and knitting to the end of the row. Turn.
casting off 8 stitches and purling to the end of the row. Turn
At the end of this... you should be ready to do a knit row and you will have casted off 58 stitches, leaving 34.
Now, it instructs you to cast off the remaining (34) stitches for the back of the neck. This would be....
On a Knit row, cast off the remaining 34 stitches.
and then i assume you will be picking those up for a neck later.
hope this helps, I tried to give you step by step in my interpretation of the directions you gave.