On the Dutch keyboard:
The '@' is in the top left corner. Use the '`' (Grave Accent) character (same key on the US keyboard) to get that character.
To put that in the table I think you would put it in character 53:
const char Lowercase = {
0, 0, 0, 0, ‘q’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, // 0-9
‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘,’, ‘n’, ‘o’, ‘p’, // 10-19
‘a’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘z’, ‘x’, ‘y’, ‘w’, // 20-29
‘&’, ‘é’, ‘"’, ‘’’, ‘(’, ‘§’, ‘è’, ‘!’, ‘ç’, ‘à’, ‘\n’, // 30-39
0, 0, 0, ’ ', ‘)’, ‘-’, ‘^’, ‘$’, 0, ‘µ’, // 40-49
‘m’, ‘ù’, ‘²’, ‘@’, ‘:’, ‘=’, 0, 0, 0, 0, // 50-59
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 60-69
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 70-79
0, 0, 0, ‘/’, ‘*’, ‘-’, ‘+’, ‘\n’, ‘1’, ‘2’, ‘3’, // 80-89
‘4’, ‘5’, ‘6’, ‘7’, ‘8’, ‘9’, ‘0’, ‘.’, ‘<’, 0 // 90-99
};
53 (0x35) is the USB keycode for the key in the upper left corner of the keyboard.
USB Scan Codes (hex)
[35][1E][1F][20][21][22][23][24][25][26][27][2D][2E][ 2A ]
[2B ][14][1A][08][15][17][1C][A0][0C][12][13][2f][30][31]
[39 ] [04][16][07][09][0A][0B][0D][0E][0F][33][34][ 28 ]
[Shift ][1D][1B][06][19][05][11][10][36][37][38][Shift ]
[ 2C ]