Originally Posted by tomtomtom123

Well, if the BB cups already have it's own dust cap with a seal, then I don't know what that spacer/washer is for. Do you know if it came with either of the cranks or with the BB?
I don't know what adapter you are using, but the 386EVO Wheels MFG adapter to 24mm spindle comes with "optional" spindle shims. You probably don't need them if your total BB width is 91mm, unless you want to adjust the chainline. Shimano road BB cups are approximately 11.5mm on each side to the dust cap, so a total of 68+11.5+11.5 = 91mm total width. You should measure your third party BB to see how wide they are, and the chainline.
https://wheelsmfg.com/tech/PDF/386EVO-SHIM.pdf





However, your FC-R7000 seems to supposedly use some kind of o-ring with the stock Shimano BBs. I have never used Shimano cranks, so I don't know what the purpose of the O-ring is and where exactly it touches. You can look at the exploded diagram to see the ring and the part number.
Y1F316000
http://si.shimano.com/pdfs/ev/EV-FC-R7000-4331.pdf


If this O-ring is sandwiched between the crank surface and the BB cup dust cap, and you're not using this O-ring, then potentially your chainline is too inward, or the splines on the left arm may bottom out. You could use those spacers that you have to push the chainline back out, or to prevent bottoming out on the spindle. You should first measure your chainline to see what it is, and check for any bottoming out. (well, very first thing to do is to check if the BB is 91mm wide) Some other photos seem to show the o-ring in a recess on the crank arm, so that it doesn't change the chainline whether or not you use it, but it probably helps to seal against water ingress onto the BB through the spindle.