[[ ((@{Level}/6)-.5)d6 ]] The number of dice rolled is rounded up when a floating point number is supplied. [[(1.5)d6]] rolls 2d6, [[(1.499999)d6]] rolls 1d6. Here's a table that shows this:
Level
/6
-0.5
Rounded
1
0.17
-0.33
0
2
0.33
-0.17
0
3
0.50
0.00
0
4
0.67
0.17
0
5
0.83
0.33
0
6
1.00
0.50
1
7
1.17
0.67
1
8
1.33
0.83
1
9
1.50
1.00
1
10
1.67
1.17
1
11
1.83
1.33
1
12
2.00
1.50
2
13
2.17
1.67
2
14
2.33
1.83
2
15
2.50
2.00
2
16
2.67
2.17
2
17
2.83
2.33
2
18
3.00
2.50
3
19
3.17
2.67
3
20
3.33
2.83
3
So, you can see that the Rounded Column will go from rolling 0 dice to 1 die at 6th level, 2 dice at 12th level, 3 dice at 18th level, etc. If you didn't subtract the .5, you'd start rolling 1 die at 3rd level. Hope that helps!!