Each history record will has 2 rows of data, 1 for Id, another for Text.
But in Report, only the Text data row will show.
In SOQL it will show both Text data and Id data rows.
So, bear in mind, if you want to count the number of history events in SOQL, you should divide the result by 2.
SELECT Count(Id), AccountId FROM AccountHistory WHERE AccountId = '001d000000AA'