Homebrew monster HP calculation incorrect

[solarisra]

Describe the bug
It appears that the calculation for the monster hit points is incorrect. As far as I can tell, this is only affecting homebrew monsters.

To Reproduce

Steps to reproduce the behavior:

1. Go to 'Monster Builder'
2. Click on 'HP Die Count' and select any number, then click on 'HP Die' and select '8'.
3. Finish building the monster.
4. Example, give a monster 5d8+5 hit points which should give a value of 27. However, it gives a value of 29.

Expected behavior

According to table on page 276 of the Dungeon Master's Guide, one would multiply the number of Hit Dice by the average for the Hit Die then round down. The example given on the page is 5d8+5 = 27, which means (5 * 4.5) + 5 = 27.5 ≈ 27.

Screenshots

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Desktop (please complete the following information):

• OS: Windows 10 build 18363
• Browser Chrome 85.0.4183.121
• Version 2.5.0.17 (7/20/2020) "Obsidian Plains Tower" edition