The Unreserve Exponent choice lets you tell the server to unreserved an exponent you
have been assigned. You might do this
if a second computer you had been running GIMPS on died or if you had been assigned
an exponent of one work type (such as a first-time-test) and now you have
switched to another work type (such as 10,000,000 digit numbers). Any work you have done on the unreserved
exponent will be lost.