ΔE 18.8, loose: different enough that you should pick on purpose. Russian AF Grey N.3 is noticeably darker than N7 Neutral Gray.
Can I use Russian AF Grey N.3 instead of N7 Neutral Gray?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Russian AF Grey N.3 is noticeably darker than N7 Neutral Gray.
Can I use N7 Neutral Gray instead of Russian AF Grey N.3?
The same difference applies the other way round: N7 Neutral Gray is noticeably lighter.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.