This message keeps appearing everytime I try to analyze my data with cellGrowth package, what does it mean? Is it a problem? How can I fix it?

Warning messages:
1: In fitCellGrowth(x, z) :
  Maximal growth reached close to the border. You can identify the well by testing for pointOfMaxGrowthRate.
2: In fitCellGrowth(x, z) :
  Maximal population reached close to the border. You can identify the well by testing for pointOfMax