Submitted by xYrYuYx
These calculations are incorrect for linear vesting.
i.e.
if start amount is 10000, and duration is 100 seconds.
After 50 seconds, user can claim 5000 which is 50%
After another 10 seconds, user need to claim 1000 which is 10%, but current calculation return 500.
Manual
Change formula to
User total amount * (block.timestamp  start) / (vesting duration)  user claimed amount.
SamSteinGG (Vader) confirmed 
