I'm trying to deal with the label 'from' in the 'add new stamp' form, see here

When I switch to Russian language that's the main language for my site I get Russian "c" instead of 'from'. It might be a correct translation but in this context it's wrong and confusing for my students, see here

However when I enter the language package editor to correct the translation the only string with the word 'from' that I get is 'givenby' that first doesn't seem to be the right one for what I'm looking for and second it has the correct translation 'от' that is not reflected in the interface, see here

Is it possible to add a correct string so that I could make a correct Russian translation myself?