Maximum allowed accumulated coin is 30 days.
can someone please explain this to me? what does it mean?
This might be for staking. Also not sure.
Yes, this means coins mature for 30 days, i.e. your staking weight gets higher and higher, making it more and more likely that the coins actually stake.
At 30 days they reach maximum maturity, nothing bad happens, it just means they reached the maximum likelihood to stake.
Note that this also means you should open your wallet and stake for a while at least every 30 days, otherwise you will miss out on staked coins. But, letting the wallet run helps the stability of the coin network, and the TOR network, so just let it run whenever you can