Refreshing is possible at sub 10.5 seconds as the refresh is based on the casted dot (ie: casting a 20Ms 35 second dot refreshes to 1.3 * 35 or 45.5 while a 0Ms dot refreshes to 19.5).
The higher-than-lvb number is 92, but there's a lower-than-lvb one too which helps reduce the Lava Burst cast delays due to the first one. With T19 2pc that lower 86 one becomes mostly irrelevant.