Customer dials 9 for out going. 8 pots lines in group.

How do I add 2 more lines to the group.

And what are the group numbers

Most likely, pool 70.

Try LinesTrunks > Pools > 70 > Enter > Entry Mode > Inspect

If you see the other 8 lines here, then back up,

Entry Mode > dial the trunk number > Enter > dial the next trunk number > Enter > Inspect

and you should see the 2 new trunks added to the pool

Thanks