Thank you for your question about Kinobi. The white material that you are seeing is normal, and it is part of the urine. In tortoises, the urine component is made up of two parts - a solid form of the urine called the urates, and then the liquid component of the urine. As long as the urine is clear and the urates are white, everything is good. You should be seeing both white and clear every time Kinobi goes to the bathroom, ideally. I did not see what species of tortoise Kinobi is, but you can also soak your tortoise 1-2 times per week in 85-90F water for 15-20 minutes per time. This will help to keep Kinobi hydrated.
I hope that answers your question, and thanks for using Petco Pet Education Center, formerly Petcoach!