g'day mate,
the measurements are in mmHG, and 760mmHG is equal to 1.0 bar or 14.3psi
so, +7 = 13.2psi
+3.5 = 6.6psi
Or take your value that you are running as 'x':
x / 7.6 * 14.3 = your boost value in psi
x / 7.6 = your boost value in bar
hope that helps,
Waz.