Spongebob

This is a welldocumented issue in Schweser and CFAI. The HP12C rounds up your N value when there is a decimal. CFAI is aware of this issue and no problem on the exam will nitpick on your choice of N.
FROM THE CFAI website FAQ:
Should I be concerned that the HP 12C automatically rounds up when computing the time required to accumulate a given future value?
No. CFA Institute is aware that the HP 12C rounds up when computing the time required to accumulate a certain sum. We have taken that into consideration in the creation of questions and in the grading process.