You could snip part of the roll and try 7 minutes. (pull out part of the roll cut it off and develop it) If that seems good then run the rest of the roll. Or if its more than one roll, snip one and then run the rest at the time you determine. You can probably judge based on the snip whether its about right or too short or too long. Lots of people expose TMax 400 at 200 so you're only one stop from that. I suspect all is not lost. If you're working on a school assignment I'd think you'd get some credit for being smart enough to salvage your work! I read once upon a time that the test of good craftsmen may not be how perfectly they do their work but rather how well they repair their mistakes.(posted 8099 days ago)