It went from +2 to +15 in my Quick analysis, but was listed as a Mistake. Screenshot: https://www.awesomescreenshot.com/image/3595748/2112c1018c8f44f57b98a8d0b2f2c209
You want to call it a blunder? Ok, by almost anyone's definition, it was a blunder.
In the Help section, they define their terms:
In the computer analysis, what's the difference between inaccuracy, mistake, and blunder?
When you are reviewing the output from a Computer Analysis of a game, it can be useful to know how terms like "inaccuracy," "mistake," and "blunder" compare to each other.
Assuming the position is roughly even (no big advantage for either white or black), it works like this:
"Inaccuracy" - The computer evaluates that this move resulted in a position that is at least 0.3 points worse than the position resulting from the best move available
"Mistake" - This move is at least 0.9 points worse than the best move available
"Blunder" - This move is at least 2 points worse than the best move available - pretty bad! :)
These values are somewhat relative to existing/previous advantages held by one player or another. For instance, if you are already massively ahead - say, by 30 points - and you make a move that drops your evaluation to +28, you're stillmassively ahead; relatively speaking, the size of your advantage hasn't changed significantly. Therefore, such a move would not be labeled a blunder.
/ So you were already losing and therefore it wasn't classified as a blunder.
It went from +2 to +15 in my Quick analysis, but was listed as a Mistake. Screenshot: https://www.awesomescreenshot.com/image/3595748/2112c1018c8f44f57b98a8d0b2f2c209