Savitas QR records are automatically deleted over time, either by the Savitas QR application or by your browser.
Each time you scan, Savitas QR compares the records on your phone with records downloaded from the server. These server records are uploaded the moment someone self-reports a COVID-19 diagnosis. Considering that we are only interested in finding out if you had a recent contact with that infected person (but, as explained, in a completely anonymous way), we only compare records from the past 10 days. If there are older records on the smartphone, they are automatically deleted at that time.
So, your smartphone holds no data longer than necessary, and does an automatic clean-up.
Apple Safari on iOS automatically deletes all browser storage older than 7 days, so on an iPhone there are no records older than 7 days since your last interaction with Savitas QR. This is however not a problem for the correct functioning of Savitas QR or the contact tracing principle: 7 days is long enough to verify if you have been in contact with an infected person.