I'd interpret that icon to mean fill the hollow .

I assume those are there for a different kit .

Assembly Instructions kit 5050 : https://www.scalemates.com/products/img/2/9/8/1310298-49-instructions.pdf

Kit 5015 : https://www.scalemates.com/products/img/9/6/2/1137962-22-instructions.pdf

Kit 5001 : https://www.scalemates.com/products/img/4/7/6/953476-38-instructions.pdf

Kit 5075 : https://www.scalemates.com/products/img/5/3/0/1351530-12-instructions.pdf

.... holy chit  , they make a lot of Tiger I kits  ,

feel free to go thru all these instructions above and below ( some are the same for multiple versions ) to find the kit that uses those indentations 

More and more Rye Tigers :

https://www.scalemates.com/search.php?fkSECTION[]=Kits&fkCOMPNAME[]="Rye+Field+Model"