Simple L a b Question

Yeah right! I have a file, supplied in USWebCoatedSWOPv2 that, when I run a dropper over it in Photoshop, appears to have a L a b value of 1,0,0 in its darkest shadow. This shouldn't be possible should it? When I convert to ISOCoatedv2 the value stays the same, which definitely shouldn't happen should it? Could anyone explain this to me?