The reply on the submitted service request:
This is a known bug which is fixed with R2019a. The bug relates to the parfor transformation in scripts. We denote synthetic temporary variables with a percent. One way to avoid having R%1 in the Workspace would be to wrap the parfor call in a function, as a function's Workspace is cleared once it returns its output. You can also simply ignore these variables as they have no impact on the calculation itself.