The instructions & photos in the kit are generalized sometimes & are shipped to more than one rifle model in their rifle lineup. In your situation, Lyman makes a 1-32 barrel GPH (and) a 1-60" barrel GPR.
I' m just guessing now, but one model may have that overextending plug & the other one doesn' t.

If you do not receive a proper response to your dilemma in the next few days, contact the manufacturer at 1-800-225-9626.