How many people were born in Russia from February 1 to February 13 in 1918?

None, because those dates never existed in Russia. Russia had been on the Julian Calendar, which was thirteen days behind the rest of the world which was on the more accurate Gregorian Calendar. By order of Vladimir Lenin, Russia switched to the Gregorian Calendar by decreeing that the day after January 31, 1918 would be February 14, 1918 thereby skipping completely over February 1 to February 13, 1918.