我正在使用下面的代码行，我试图减去两个结果以得到第三个结果，但是我收到了一个错误。请告诉我如何在Pug中进行减法。
代码：
mixin dispatch-summary(dispatched)
- var count = 0
table
caption.align-left.font-bold DISPATCHED RECORDS
tr
th.align-center.font-bold S.NO
th.align-center.font-bold Dispatch Id
th.align-center.font-bold Projects
th.align-center.font-bold HardwareBoxes
th.align-center.font-bold PanelBoxes
th.align-center.font-bold TotalParts
th.align-center.font-bold DispatchedParts
th.align-center.font-bold PendingParts
th.align-center.font-bold TotalHardware
th.align-center.font-bold TotalHardwareDispatched
th.align-center.font-bold TotalHardwarePending
each task in dispatched
-var dispatch_id= task.dispatch_id
-var project = task.project
-var hardware_boxes = task.hardware_boxes
-var panel_boxes = task.Panel_boxes
-var total_parts = task.total_parts
-var dispatched_parts = task.dispatched_parts
-var pending_parts = (task.total_parts)-(task.dispatched_parts)
-var total_hardware = task.total_hardware
-var total_hardware_dispatched = task.total_hardware_dispatched
-var total_hardware_pending =(task.total_hardware)-(task.total_hardware_dispatched)
tr
td.font-bold=++count
td.align-left= dispatch_id
td.align-left= project
td.align-left= hardware_boxes
td.align-left= panel_boxes
td.align-left= total_parts
td.align-left= dispatched_parts
td.align-left= pending_parts
td.align-left= total_hardware
td.align-left= total_hardware_dispatched
td.align-left= total_hardware_pending
注意：在上面的代码中，我想减去total_parts和dispatched_parts以获得总数pending_parts
-var pending_parts =（task.total_parts） - （task.dispatched_parts）