Let the user names represent their quantities of clicks. The table below lays out the given information:
The columns in the body of the table create equations:
Operating Systems: A+F=10, B+D=25, C+G=10, E+H=5
Browsers: B+F=10, A+C=20, D+H=10, E+G=10
Devices: B+C+D+G=21, A+E+F+H=29.
We appear to have inconsistencies. If B+D=25 and C+G=10 then B+C+D+G=25+10=35 (OS).
However, B+C+D+G=21 (devices).
Also: A+F=10 and E+H=5 so A+E+F+H=15 (OS), but A+E+F+H=29 (devices).
The discrepancies amount to 14 clicks in each case.
Because of these discrepancies I can only try to provide a solution which ignores the given device counts but permits the OS counts.
The device counts adjusted are 15 for mobiles and 35 for desktops. These add up to 50 clicks.
Please correct the inconsistencies.
The smallest total is E+H=5, so E=5-H (0≤E,H≤5);
E+G=10, so 5-H+G=10, G=H+5 (5≤G≤10);
C+G=10, so C+H+5=10, C=5-H (0≤C≤5);
A+C=20, so A+5-H=20, A=H+15 (15≤A≤20);
A+F=10, so H+15+F=10, F=-5-H (F<0). None of the click counts can be negative.
There can be no solution unless the information is incomplete or incorrect.
If we replace all the totals with the initial letters (lowercase) of the browsers and operating systems we get:
E=i-H, E+G=o, i-H+G=o, G=H+o-i;
C+G=l, C+H+o-i=l, C=l+i-o-H;
A+C=c, A+l+i-o-H=c; A=H+c+o-i-l;
A+F=a, H+c+o-i-l+F=a, F=a+i+l-c-o-H (a+i+l=25, c+o=30, resulting in F<0);
B+F=b, B+a+i+l-c-o-H=b, B=H+b+c+o-a-i-l;
B+D=w, H+b+c+o-a-i-l+D=w, D=w+a+i+l-b-c-o-H;
D+H=e, so w+a+i+l-b-c-o=e, or w+a+i+l=e+b+c+o=50 (as expected).
Also, A+E+F+H=a+i, B+C+D+G=w+l.