Issue with duration when export to musicxml

There is Chopin - Nocturne Op. 9 No. 1 in 3th measure we have polyrhythm 11 to 6.
When export to musicxml the divisions is 480.
And the 11th has duration 131. The quarter has 480 and the half has 960.
11 * 131 + 480 + 960 = 2881
When divisions is 480 the measure total duration should be 480 * 6 = 2880.
From first sign look like divisions should be 6 * 11 = 66 and duration for notes:
half: 66 * 2 = 132
quarter: 66
11th: 18
Then total measure duration: 396