Congrats on getting losing again! I have just about 100 lbs., maybe a little less to lose altogether and I have days where I think, "I don't know how I'm going to keep at this, with this level of commitment, for another year!" Keeping going is an achievement itself.

I'm not familiar with FitDay, so I'm not sure what your options are, but here are several ways of writing your height:
5'0.5"
5'.5'
5'1/2"
5-.5
5-0.5

But my guess is that you need to round to whole numbers. The calculator may not allow you to put partial inches. So you'll have to tell it you're 5'1" or 5'0".