You should stick to float() to convert your strings. Don’t rely on the Panel component to show sane values for these numbers, as you’ll get all sorts of automatic representation shortenings that lie about what they represent.
As already alluded to in your other thread, Panel isn’t a good component, especially not to pipe your data through. You can use it to show data, but you shouldn’t put it between components.
Just simply use float() and check the actual data. You’ll see that you get the data you need.
See how the output of the Expression component gives you exactly (well, exactly enough, IMO, there still is some rounding going on) what you have in the data, that was also print()ed to the python output console.