Intuitive rather than rigorous

"Problem solving, making reasonable assumptions may become harder if we become conscious of the process. Thus rendering one's thought processes explicit, or analysing a judgment, may actually impair performance, because it encourages the left hemisphere's focus on the explicit, superficial structure of the problem." (The Master and His Emissary, Iain McGilchrist, 2009; page 65). 

"It is worth considering that numbers can either signify absolutes – a quantifuable amount, as in statistics – which would suggest an affinity with the left hemisphere, or signify relations, which would suggest an affinity with the right hemisphere. For Pythagoras, it was this regularity of proportion or relationship, rather than number in any absolute sense, that underpinned music and beauty – the music of the spheres, the natural harmony of the universe." (The Master and His Emissary, Iain McGilchrist, 2009; page 66). 

Imprecise estimates of size are matters of relation, not precision. They are intuitive rather than rigorous; organic, not mechanical.