The default scale used in the tune finder is 0.65, which comes out on paper as a moderately small scale with a lot of notes per staff line. A scale of 0.40 would be a bit too small for someone to read at the distance of a typical music stand, but might work well if you're playing flute or piccolo in a marching band with the music close to your face. A scale of 1.00 would be quite large, good for many musicians with poor eyesight, or on a typical A8 or Letter page size held up for a large room to see.
Different ABC-to-staff-notation programs typically have somewhat different values for the scale factor, but the above is fairly typical.
For various portable gadgets with small screens, the size of the formatted music will vary, depending on how the browser or PDF display app was written. There really isn't much in the way of standards for such things yet.