The 1st column has the names of Pokémon that, in Red and Blue versions, are only obtainable in two places. This includes finding them in grass, by surfing, or fishing. In-game trades are specified.
To make a guess, type the name of the Pokémon followed by its first location in column 2 and its second location in column 3. So for example, if Diglett were only found in Diglett's Cave and Route 7, and Diglett's Cave were in Column 2 and Route 7 in Column 3, you would type "Diglett Diglett's Cave Route 7". For trade locations, only type the city.