My first thought is a Join creating duplicate entries but without a workbook or any other info, it's just a guess.
There is no join other than Tableau is directly pulling the data from HANA.
Problem is ASA data is coming on tableau it is showing more number of rows than HANA.
Hmm....well if there's nothing manipulating the data in Tableau, maybe it's an issue with Tableau interpreting the data. Is there any problem with drivers? Do you have this problem with other HANA data sources or just this one? This is almost sounding like a translation problem between the data source and Tableau. This is a bit of an odd one and you may need to engage Tableau Technical Support to narrow it down further.