I am adding this using my mobile and I don't see any spoiler button, so the mod may please put this in a spoiler.
Here is a general method to solve for more possibilities

For starters:
the second and third words seem to suggest "google batman"... last word of first line could be "looks".
similarly, the second line suggests to "google" something...
can you send a screen shot of where and how this phrase is written. That might contain more clues...
The idea here would be to google some keywords and find the answer to your puzzle.

You assume a constant rate of growth of grass over the entire duration.
I'm not sure about this and pls correct me if I am wrong: If some grass is eaten on any given day, shouldn't the rate of growth of grass be slower the next day?