During the activity transfer process, some data is lost

I created two activities and tried to connect them in a workflow.
The role of activity1 is to read data from a csv file and return data in type [pandas.core.frame.DataFrame]
while activity2 is to process data in type [pandas.core.frame.DataFrame].

However, I found that a two-dimensional dataframe is always truncated and only the first row of data is returned.