hi @VictorMaeda
Go through the below link to debug your codes. A feedback information like yours is probably trying to check if you are implementing your time series function correctly, like using len function instead of using the assignment recall function to define a give period.
After going through the post, if you still encounter the same feedback, then click on my name and then message me screenshots of grade function cell.
Make sure not to post any grade function codes here as it is against community guidelines to post on public post thread.
Regards
DP