This is an entry for the 16th Fortnightly Challenge.

You won't believe what happened at work today! I was working on a new software when Robert, the colleague I work with on this, got mad in a second : he banged his table, shouted the f-word and left the office! Well, one thing I know is that he was not really working on the software... All the morning, I've seen him writing things on pieces of papers. That's why once he had left, I went to his desk to understand his rage. Before he came back, I was able to take a glimpse at this piece of paper.

At first, I was... puzzled. But then I remembered where I had seen this grid before. I smiled.

And you, can you find out why Robert left in anger?

• Looks a bit like a game of Minesweeper, but some of those numbers are far too big. – Rand al'Thor Sep 21 '16 at 12:32
• @randal'thor The numbers appear to be an ordering rather than relevant to potential other content/meaning in the grid – Will Sep 21 '16 at 12:39
• @ABcDexter It is! If you look at the chat, Will has the right answer, but I'd like a more complete answer from him :-) – IAmInPLS Sep 21 '16 at 18:25
• @IAmInPLS Ok, great. Then this is the most awesome puzzle for my return :D thanks :) – ABcDexter Sep 21 '16 at 18:27
• Wouldn't square 17 and 18 have been revealed already when you click on square 1? – Kruga Sep 26 '16 at 7:59

rand al'thor points out that

This is a 9x9 grid like Minesweeper

and since

the numbers 1 through 16 are present along with 8 Xs

the numbers are

the order in which Robert clicked the squares in his Minesweeper game

but after the square marked 16, Robert's got this (image courtesy of OP)

and we can now see why Robert is distressed:

Robert is left with a 50/50 chance at winning the game (hence the ?s) since there are two mines left to find and the top right corner thus has two possible solutions:

1 2 ? ?
X 3 ? ?
- X 2 1
could be either of these

1 2 X 2    |    1 2 2 X
X 3 3 X    |    X 3 X 2
- X 2 1    |    - X 2 1

... which is a situation that always frustrates me, though I don't get quite as angry...