I have data written in Delta on ADLS. As I understand the delta also internal file in parquet format but when Iread the file in different format I got different record count

spark.read.parquet()

 or 

spark.read.format('delta').load()

df = spark.read.format('delta').load("data")
df.count()
> 200000
 
df = spark.read.parquet("data")
df.count()
> 400000

As you can see the difference is quite big.

Is there something I misunderstood about delta vs parquet?