Bug with heatmaps

Hi, I have been experimenting with the new heatmap facet in solr 5. When I use grid level 6 I notice a bug.

with level 7, I get for example
rows: 6
cols: 26
XmaX: 10.7514953613 Xmin 10.7157897949
YmaX: 59.9317932129 Ymin 59.9235534668
Cell size
0.00137329101562 x 0.00137329101562

with level 6
rows: 11
cols: 26
X maX: 10.8435058594 Xmin 10.5578613281
Y maX: 59.9468994141 Ymin 59.8864746094
Cell size
0.010986328125 x 0.0054931640625

notice the cell size
I could be that my code is faulty, but this works for all other grid levels