Sorry for not providing much info before.
Phabricator has a floating point issue when adding up decimal task points.
I can reproduce this by putting tasks with the following point values (in this order) on a single workboard:
0.1, 0.25, 0.25, 0.5, 0.1
The total shows up as:
Maybe should just find whatever the longest decimal component in the list is and round to that.