Mass of glass calculated inaccurately

I can't build a Solar Panel despite having exactly 200 kg of solid glass in a container nearby.

There are no ordered constructions using glass, so it isn't reserved.

However, the container it is stored in shows only 199 kg of storage is used, despite 200 kg glass sitting in it.

Is it just a calculation / display error, or is it possible some microscopic amount of glass was lost during the cooling of liquid glass to a solid, and some labels round it up to 200?

If this might be relevant, this is my glass production for now:

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The room isn't filled with steam yet, its vacuum most of the time. The liquid glass drops into the water below. When it solidifies, it's picked up by an auto-sweeper and it runs on a conveyor loop until it cools down below 125℃, at which point it's moved to a conveyor chute by the entrance lock.

I've also managed to construct 8 solar panels before this happened, so I've made at least 1600 kg of glass without the problem becoming noticeable.