Hi,
Currently there is no way to have a percentage witdth with correct rows count, but there will be in the upcoming release, as we update the script to calculate based on visible item values in stead of the defined ones. The item width input will also be changed to accept a percentage value as well.
The rows count simply indicates how many rows of items there should be before starting the pagination. The problem here is only the percentage width, as the calculation uses the initially defined pixel width. It will display the items fine, but the rows count will be incorrect.