Hi Manish ,
The "=" is used to signify that what is in J3 and K3 is to be used a text , and not as criteria.
You are having the data >4-5 as a text string in your column B ; within the SUMIFS , if you do not use the construct "=" & J3 , then using only J3 makes the SUMIFS take >4-5 as the criterion , which means your data should be having only the text string 4-5 and the criterion becomes greater than 4-5.
Using the construct "=" & J3 makes the SUMIFS take the data in J3 as a text string and the criterion as equality. What ever text you enter in J3 will be treated as text , and the criterion will always be equality.
Try entering all the different values you have posted in J3 and K3 and see for yourself. Thus , entering >6-7 in J3 and <=75 in K3 will give you the result 80.
Narayan