Reproduce steps:
1, create a vessel simply with only one part, which is "Solid Rocket Motor[Procedural]" (aka. ProceduralSRBRealFuels)
2, limit the solid fuel amount to less than 100%, e.g. 60%
3, launch vessel
4, check part's "burn time" item, now it's "30s"(default value)
5, hit ESC key, select "Revert to Launch"
6, check part's "burn time" item, now it's "50s"
7, repeat steps 5 and 6, the "burn time" is larger each time
Reproduce steps: 1, create a vessel simply with only one part, which is "Solid Rocket Motor[Procedural]" (aka. ProceduralSRBRealFuels) 2, limit the solid fuel amount to less than 100%, e.g. 60% 3, launch vessel 4, check part's "burn time" item, now it's "30s"(default value) 5, hit ESC key, select "Revert to Launch" 6, check part's "burn time" item, now it's "50s" 7, repeat steps 5 and 6, the "burn time" is larger each time