another transaction error message and strange math

thanks for all your work on this very timely solution to some of the economic problems we're facing.
the default currency for my site is quarters of an hour. if any number is in the quantity field and "00 hours" is selected in the quarters field (i'm guessing this is there to allow transactions which involve whole hours), there is an error message which tells me i must enter a positive number. if i hit save again without changing anything, the transaction either goes through or goes to pending, depending on what is selected. my balance updates to u looking symbol-1 (i'm guessing it symbolizes a quarter hour?). shouldn't this be -4? if i conduct a transaction for 1 45 minutes, i get the same error message saying i must enter a positive number and the quarters field is back to 00 hours. if i then select 45 minutes again, my balance updates to -2. should this not be -3 since 45 minutes is 3 quarters of an hour? a transaction of 1 30 minutes results in -2 as well. i also noticed that if i go back in to edit the transaction, 1 45 minutes or 1 30 minutes becomes 2 00 hours.