spark UI about file size read

I run this sql 

select * from cm_dw.dwd_client_install where proc_date=20220707;

and then see the SQL page , it shows  the file size read: 2.1MB,it is right,the file on my storage is 2.1MB,

but The Stages tab  shows input size:4.3MB, I dont kown why it is not equal 2.1MB.

and I run this sql on spark 2.3.3,  Stages tabs shows input size:2.1MB,also right!