The Roshi explains that the calligraphy is written including the sky and the earth by arranging the charcters in this way.
Above you have the blue arrow following the characters 萬里無雲萬里天 Read from left middle around top to right middle: Banri kumo nashi banri no ten 10000 miles no cloud, 10000 miles sky.
Following the green line the characters, read from left middle down to right middle: 千江有水千江月Senko mizu ari sen ko no tsuki 1000 rivers of water 1000 moons reflected in the river.

Together forming a circle, symbolyzing heaven and earth.