SQL Rebuild indexes data size percent a little smaller I see a small change int the percent of data when rebuilding. I feel that this might be a usual issue but as I am new to SQL I get little worried when I see that the percent of data goes down after running the rebuild. I used the data usage report to get the percent of data.

I think what happen here is that some data got reorder during the index rebuild. Which in turn free up a small percent of space. I was not expecting this because my research did not indicate that this would happen. That is why it got me worried that there might be data loss.

I have confirmed from a good copy of the db that the number of records is either the same or garter in the copy where I rebuilt the indexes. Let me if I'm wrong.
SQL Server Internal Fragmentation is caused by pages that has too much free space. for example at the beginning of the day we have a table with 50 pages that is 100% full, but by the end of the day we have a table with 60 pages that is only 80% full because of various delete and insert statements throughout the day. This may lead to a decrease in performance because now when we need to read from this table we have to scan 60 pages instead of 50. Index maintenance tool and additional information here.