Uniden GMR3740 Radios 16 Hour Charge Time

So the manual describes the charging procedure however it still leaves me with questions after reading it. It says to charge the radio plug in the 9V vehicle adapter and charge until the charge indicator stops flashing. It goes on to say that charge time may vary depending on how discharged the battery is. Ok that is simple enough I get that. Though when it talks about charging the radios in the charge cradle that is what I DO NOT understand. It says to place the radios in the cradle and charge for 16 hours. Then remove the radios from the charger. So does this mean that if left in the charger the radios could potentially over charge? There is no indication that the charger will shut off. Is it such a slow trickle charge that it does not matter? Anyone know. The directions for charging with a vehicle adapter is simple enough (adapter not included) But the directions for charging with the cradle is sketchy.

Uniden GMR3740 Radios 16 Hour Charge Time