Here is a solution for you that takes the list of browser sizes and if there are duplicates creates a list of unique sizes and gives the total for all browser sizes that have a dimension of 1000 or more in either length, width or both.
The solution uses a helper column to determine the dimensions and returns. I used text values to make it obvious what the results were. You might prefer something else:
lessless if both dimensions are < 1000
lessgreater if the first dimension is less than 1000 and the second dimension is >=1000
greaterless if the first dimension is >1000 and second dimension is <1000
greatergreater if both dimensions >=1000
Helper column:
Formula:
=IF(--LEFT(B4,SEARCH("x",B4)-1)<1000,"less","greater")&IF(--(RIGHT(B4,LEN(B4)-SEARCH("x",B4))*1>=1000),"greater","less")
Unique browser sizes:
Formula:
=IFERROR(INDEX($B$4:$B$20,MATCH(1,INDEX((COUNTIF($H$1:H3,$B$4:$B$20)=0)*($B$4:$B$20<>""),0),0)),"")
Count for browsers with a dimension >=1000
Formula:
=IF(H4<>"",SUMPRODUCT(($B$4:$B$20=H4)*($D$4:$D$20={"lessgreater","greaterless","greatergreater"})*$C$4:$C$20),"")
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