Questions about 'get_feature_config' function in class HighFreqGeneralHandler

[caozhenxiang-kouji]

When I run the follwing code
python scripts/gen_pickle_data_hsm.py -c scripts/pickle_data_config.yml
, I print out the generated results of self.get_feature_config() in class HighFreqGeneralHandler. The results are as follows:
['Cut(FFillNan(If(IsNull($open), $close, $open)/DayLast(Ref(FFillNan($close), 480))), 480, None)',
'Cut(FFillNan(If(IsNull($high), $close, $high)/DayLast(Ref(FFillNan($close), 480))), 480, None)',
'Cut(FFillNan(If(IsNull($low), $close, $low)/DayLast(Ref(FFillNan($close), 480))), 480, None)',
'Cut(FFillNan(If(IsNull($close), $close, $close)/DayLast(Ref(FFillNan($close), 480))), 480, None)',
'Cut(FFillNan(Ref(If(IsNull($open), $close, $open), 240)/DayLast(Ref(FFillNan($close), 240))), 480, None)',
'Cut(FFillNan(Ref(If(IsNull($high), $close, $high), 240)/DayLast(Ref(FFillNan($close), 240))), 480, None)',
'Cut(FFillNan(Ref(If(IsNull($low), $close, $low), 240)/DayLast(Ref(FFillNan($close), 240))), 480, None)',
'Cut(FFillNan(Ref(If(IsNull($close), $close, $close), 240)/DayLast(Ref(FFillNan($close), 240))), 480, None)',
'Cut(If(IsNull($volume/Ref(DayLast(Mean($volume, 7200)), 240)), 0, $volume/Ref(DayLast(Mean($volume, 7200)), 240)), 480, None)',
'Cut(If(IsNull(Ref($volume, 240)/Ref(DayLast(Mean($volume, 7200)), 240)), 0, Ref($volume, 240)/Ref(DayLast(Mean($volume, 7200)), 240)), 480, None)'
], ['$open', '$high', '$low', '$close', '$open_1', '$high_1', '$low_1', '$close_1', '$volume', '$volume_1']

I has 2 questions here:
First, I believe the variable 'day length' in class HighFreqGeneralHandler should be divided by freq. In my case, the freq is 5 min, so a day only has a length of 48. The Ref($close, 480) here just indicates the close price 10 days ago.
Second, the actual usage of function 'get_normalized_price_feature' is inconsistent with the annotations here. However, it seems that the open,close,high,low of today will be divided by the close price 2 days ago, and the those of yesterday will be divided by the close price of yesterday(and then Ref again? I don't know why). I 'm a little confused here and is looking forward for a more detailed explanation.