fixed typo in CoU

efficiency_module/static/efficiency_COU.md

@@ -25,5 +25,5 @@ The tool is limited by the assumptions upon which the model is based.  The salie
 
 1. The extractable is macroscopically homogeneous within the matrix.  Therefore, the output is only applicable to compounds that are introduced either intentionally or unintentionally during synthesis (e.g., residual monomers and oligomers, catalysts, initiators) or compounding (e.g., stabilizers, antioxidants, plasticizers) are within scope. The model is not appropriate for surface residuals from processing, cleaning, and sterilization. 
 2. The solvent is "perfectly mixed".  This should be a reasonable assumption provided the samples are adequately agitated in a static bath over the timeframe of the testing.  However, this assumption may not be appropriate if sufficient agitation is not applied and a boundary layer develops that slows the release rate or if the extraction is conducted under flow conditions.
-3. Possible chemical reactions are not considered.  Therefore, if the polymer matrix undergoes substantive degradation during during the extraction test, the predictions may not be relevant.  Further, the model does not consider the potential for individual extractable compounds to degrade.
+3. Possible chemical reactions are not considered.  Therefore, if the polymer matrix undergoes substantive degradation during the extraction test, the predictions may not be relevant.  Further, the model does not consider the potential for individual extractable compounds to degrade.
 4. The test article is comprised of a single polymer matrix.  In practice, complex devices may be comprised of multiple components and/or polymer matrices.  In these scenarios, careful consideration of the potential contributions of each material constituent of the test article to the extractables profile is critical when attempting to leverage the model predictions.