Weird SUM calculation results

Hello Wapplers,

I have pretty basic repeat where I’m calculating work hours and then after repeat I’m calculating SUM of those works.

repeat_calculation.sum(‘calculation_man_hour’)

But I see that calculation results are weird:

“repeat_calculation”: [
{
“job_id”: 1,
“calculation_man_hour”: null,
},
{
“job_id”: 2,
“calculation_man_hour”: “28.81”,
},
{
“job_id”: 3,
“calculation_man_hour”: “95.79”,
}
],
“total_man_hour”: 124.60000000000001,

I’ve highlighted number that I’m calculating with SUM and exact SUM with bold.
Is there something I should additional tweak the SUM? This happens because of NULL result in one of the entries?