Hey @ximenling20, the AggregationsHelper is missing a method for SerialDifferencing(); I'll add one now.
In the meantime, you can get the value as you have done
You could also get it with
if (item.Aggregations.TryGetValue("serial_diff", out IAggregate aggregate))
{
var serialDifferencingAggregate = (ValueAggregate) aggregate;
}