Seems you might have to tell the program that 1/2 is suppose to mean .5. Otherwise, it is just guessing. When I enter 1/2 into a popup, it is recognized as a date (Jan 2).
You can tell it that you want it as a fraction by formatting cells as Fraction, then select the cells and format as popup.
So, try putting the fractions into cells first (make sure to format as Fraction). Then select the cells and now format them as Popup. All the selected cells will have popups populated with each fraction and recognized as such. From here, you can copy and paste them to where you want them.
Seems to work well for me.