I think it depends on what this means. I think it'll be the first sentence, but it's not really clear.
a quarter of the depth of the measuring cup?
a quarter of the depth of the container the liquid is in?
the depth of the size of a US quarter ($.25)?
What?
The liquid should be scooped at a quarter depth.
or
The liquid should be scooped at a quarter depths.
Which is correct?
2 answers
The liquid is to be scooped at a quarter of the depth of the container holding it is in. Hence the first sentence is correct? Or is there a better way of phrasing?