I think that feDropShadow primitive is the problem : it isn't recognized by inkscape. Select with objects panel (ctrl+ shoft + L) the three texts and do Filters > Remove filters.
Then you can :
rebuilt teh filter with filter editor (feDropShadow is actually a shortcut for a list of primitives as shown in link)
use the Filters > Shadows and Glows > Drop Shadow instead.
or use a blurred clone (better, apply a clone LPE to the text)
Beginners' Questions Inkscape does not render filtered text
Inkscape.org
I've been trying to load this into inkscape to convert it into png, but the text does not load. It also fails to load in other png convertors online.
I think that feDropShadow primitive is the problem : it isn't recognized by inkscape. Select with objects panel (ctrl+ shoft + L) the three texts and do Filters > Remove filters.
Then you can :
Take a look at this in-depth tutorial about filters, by Mark.
I'd put a blurred slightly transparent duplicated text object with an offset under the numbers as a shadow shape.
The advantage of filters is that you can still edit the numbers.
As a blur remains a bitmap filter, I think it's more practical to use an svg filter rather than an LPE clone on a text, and then blur it.
A LPE is inkscape-dependant, if I don't misunderstand things (I won't display correctly on a browser, for example).
I attached the original file with a modified filter.