u/Avocado-Timely

I filed a claim for IBS under gulf war presumptive. It initially was denied due to them applying the wrong legal standard. I had a higher level review and I was service connected at 10%. the rational was I only had pain related to defecation once In the last 3 months, when in reality it is nearly daily. I explained that in my HLR as well as my lay statement. My question is, will filing a supplemental claim for an increase backdate to when I initially filed my intent to file? This is about 5K I would be leaving on the table otherwise.