I&O and weighing diapers

I'm a student and I am currently in my pediatric rotation. My patient was a child who was potty-training so she wore diapers but at other times used the toilet. When recording I&Os I questioned how to document the weight of the diaper so that it was obvious that it was weight and wouldn't be confused with mls of urine. I was told that weight in grams equals mls and I should document it the same without any special notation needed. I was surprised by this and wanted to look more into it, but I haven't been able to find documentation so I wondered what your practice is and where I could find more information about this.Thanks.