Sevin 32oz Squeeze-&-Pour bottle: Bad design?

This is the red bottle of concentrate where you squeeze the bottom chamber to fill the upper 3-oz "measure" chamber.
Works fine, but suppose you have /more/ than 3-oz of product you want to put back into the bottle? How on earth are you supposed to move the contents of the filled upper chamber back down to the bottom so you can put more in the upper chamber?
The only way I can see is to drill out the plug that GardenTech uses to seal the bottom chamber from the upper chamber. The instructions do not mention this issue. Am I missing something obvious?

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