I’m stealing @garethrking’s answer from another thread ( Position of the adjective mân) here -
" Generally when mân precedes the noun it has the meaning of ‘slight’ or ‘insignificant’, while its more concrete meaning of just ‘small’ generally follows. So if you can replace ‘small’ with ‘slight’, then mân in front. That’s my impression with this word.
So:
mân wahaniaethau small (= slight) differences
but not
*mân adar small birds , because they are not ‘slight’ birds, are they?
Similarly (for example) arian mân small change , but mân donnau small waves (because they are slight on the surface). "