I have a bottle of hair styling gel that says is it 3.59 oz (100 ml). The TSA allows you to have 3.4 oz (100 ml) liquid containers. The people who made my gel incorrectly converted one way or the other. Will they allow it since it is 100 ml or disallow it since it says 3.59 oz?
Well TSA is a US agency so they'll be going my Imperial sizing. But they're not SUPER crazy checking the exact volume of bottles. My rule of thumb is basically is it bigger than a bottle of hotel shampoo? Anything about that size is A-OK. Yes its smaller than 100mL usually but its a safe bet it will travel. Also if it's sold in the travel section of a drug store, it's a good bet it will travel.
Also helpful tip, put all those liquids and gels into a clear ziplock back and put it through separately at security. Makes it easier for them and they get less picky. The easier you make their job the easier they are on you... generally.
There's no way of telling really. If the bottle looks too big, they'll discard it. If it looks like around 100 ml, the official will look at the contents labeled on the container.
My metric European mind says they'll look at the 100 ml (easier to distinguish) but when you've lived with US fluid ounces all your life you might as well have 3.4 burned into your mind (not the 3.59 imperial fluid ounce). So in that case seeing 3.59 will be reason for dismissal.
Once a TSA officer has made a decision they generally don't bargain. Specifically not about containers not being full. They may be sensible to that, but don't count on it.
So, as Michael hampton commented:
Put a sticker over the "3.59" so that only "100 ml" is visible. Sorted.
Or leave the container at home.
Or take a smaller travel bottle and put in what you expect to use.