I got "ERROR Correct answer : 10.0 s outside limits of true value" when I used calculated answer in questions although it is within the limits.

I'm using Moodle 2.7 at Helsinki Metropolia University of Applied Sciences.

Here are steps to repeat the problem:
1. Create a new Calculated question.
2. Give

• Name and description (what ever)
• Answer formula: 60 / ( {rpm1} - {rpm2})
  - Grade: 100 %
  - Tolerance: 0.1, nominal
  - Answer display: 2 decimals
  - Unit handling: The units must be given
  - Units: s, multiplier 1.0
  Save changes
  3. Give:
  - Wild card {rpm1}

  : will use the same existing private dataset as before

• Wild card {rpm2}: will use the same existing private dataset as before
  - Do not synchronize
  Next Page
  4. Give:
  - Wild card {rpm1}: 570, min: 565, max: 575, Decimal places: 0
  - Wild card {rpm2}

  : 560, min: 555, max: 564, Decimal places: 0
  Update the answer tolerance parameters
  ==> Correct answer: 6.00 s inside the limits of true value
  Add 20 new set(s) of wild card(s) values

ERROR:

Wild card

: 569
Wild card

: 563
60/(569 - 563) = 10.00 s
ERROR Correct answer : 10.00 s outside limits of true value
Min: 9.90 s — Max: 10.10 s