revise docs for percent
revise docs for percent

the greater than was backwards, thanks gil-c

see https://github.com/libvips/libvips/issues/1560

lovell/libvips,jcupitt/libvips,lovell/libvips,lovell/libvips,jcupitt/libvips,jcupitt/libvips,jcupitt/libvips,lovell/libvips