Can someone translate an equation so it makes sense to me?

Hi All,

A few of my posts back, I had asked for help with a formula. I received a formula that did what I want, but now I would like to understand what it means. If someone could break down the following formula so that I can understand it for future use it would be greatly appreciated.

{=IFERROR(SMALL(IF(COUNTIF($M$2:$M$28,'Open Order'!$G$2:$G$5000)>0,ROW('Open Order'!$G$2:$G$5000)-ROW($I$2)+1),ROWS(D$3:D3)),"")}

To save some time, let me explain what I already understand.

{} means it is an array.
IFERROR(,"") leaves a blank if the formula does not come up with an answer.
The formula is using M2:M28 as its reference.
The formula is searching Open Order!G2:G5000 to see if it matches anything from M2:M28.
>0 I am assuming grabs anything greater than 0.
+1 I am assuming adds 1 to the number it generates.



Thank you