I am familiar with that area.
Actually, the light grey areas appeared when I did a copy, paste of first 8 bars to end of 32 bar song. (Could not see how to use repeat here to do it - I CAN use repeat to duplicate bars at end of song to continue repeating there but not for earlier bars to be put at end - here I use copy,paste).

Would like to know how to delete those useless light grey bars.