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

ROW('Open Order'!$G$2:$G$5000)-ROW($I$2)+1) is just to give an array of numbers starting from 1 the same length as $G$2:$G$5000 which is 499 rows 1:499 ie {1,2,3,4.......,498,499}
row('Open Order'!$G$2:$G$5000) is equal to row(2:500) you need 1:499
so whomever wrote that formula deducted row(i2) from that ie 2
giving row(0:498) then added back on the 1
row(0:498)+1 =row(1:499)

a lot of people do this as its thought by some that its easier to reproduce,especially by users who are not quite sure how it works
eg For range X17:X99 you would see row($X$17:$X$99 )-row($x$17)+1 instead of just row($1:$83)