The lowest positive value for Gravity that can be entered that will still allow the player to jump is 0.0030612244302160997

Any value below this that isn't negative will prevent jumping. (I.E. 0.003061224430216099 )

Additionally, 0.00306122443021609901 to 0.00306122443021609904 rounds down to 0.003061224430216099, 0.00306122443021609905 to 0.00306122443021609948 rounds to 0.0030612244302160993, 0.00306122443021609949 to 0.00306122443021609991 rounds to 0.0030612244302160997, 0.0030612244302160992 to 0.0030612244302161003 rounds to 0.0030612244302161, and so on with further odd rounding rules.