What is the syntax for averageif?

I have a table tracking gas prices week to week, and another projecting gas expenses by month. I have algorithm =SUM(AVERAGEIF(N2:N35, “<>o”)*4)-H20)

That calculates the average weekly fill up cost, ignores cells with a value of 0, multiplies the results by 4 (week to month), and subtracts any weeks that already happened from the projected monthly total.

Now I want to alter that from ignoring 0 to only consider cells with a greater 30 value, trying to future proof the algorithm from considering weeks where I have pto or holidays and thus don’t burn gas commuting in; but I don’t understand the arguments for the average of or how to change them. If I’m not mistaken right now it’s just ignoring 0 like it’s a text string?