Basking time?

Red eared slider. 19 years old.

Spent last three days frantic swimming and attempting to escape. Found out nitrate was at 80 ppm so I did a water change. Also lowered temp of water to 76-77. Around 12:46 she got onto the platform and fell asleep for 2 hours. Then she’s been awake and moving but still on the platform.

Now she’s pancaking with front claws dipped in water, head resting above the water level and rest of body on dock with back legs splooted out. She’s been up there for 3.25 hours, and I know they can bask long. I also know she hasn’t basked for the last three days (other than when I put her in the nesting box for 2 hours each day but she spent a chunk of each session moving around and not basking) and is more than likely catching up on uvb/heat.

Question: is the 3.25 hours excessive or given the circumstances and normal facts, is it normal? Thank you all