You are right to think about Uttam Shama in relation to Daslakshan, but Uttam Shama is not the last day of Daslakshan.

• In the Digambar Daslakshan Parva, there are ten days, each named after one Uttam (supreme) virtue. Uttam Shauch (Purity) is the 4th day, not the last. The last (10th) day is Uttam Brahmacharya (Supreme Celibacy/Chastity). ( jainknowledge.com)
• For Shwetambar practice, the related festival is Paryushan, which is typically about 8 days long and ends with Samvatsari (the day of forgiveness). The framing and sequence of Daslakshan are treated differently in Digambar and Shwetambar communities. ( parasnathjainsociety.org)

Key points:

• Uttam Shama is not one of the ten listed Daslakshan virtues in the Digambar framework; the corresponding virtue is Uttam Shauch (Purity) as the 4th day. If you meant forgiveness, that’s Uttam Kshama, which is Day 1 of the Digambar Daslakshan Parva. ( jainknowledge.com)

You can read more about the ten virtues and their order here:

• Uttam Kshama, Uttam Mardav, Uttam Aarjav, Uttam Shauch, Uttam Satya, Uttam Sanyam, Uttam Tap, Uttam Tyag, Uttam Akinchanya, Uttam Brahmacharya.