There are a few known issues with the current EV graph - this is just an introduction to the full EV functionality to come. When it is updated and the EV calculations are done at import time and stored in the database they will be made as accurate as possible.
That said, if this is a simple 2 player all-in situation then please attach the hand history file to a
Support ticket and identify the relevant hand so that we can investigate.
Thanks.
For now you should use the Replayer's Win% to analyse EV for individual hands.