I would say sealed, it is an AGM Battery. From the manual;
8.2 SELECT BATTERY TYPE
The Battery Type rotary switch allows selection of 1 of 3 charging algorithms. These are broadly defined as the following battery types as noted on the lower label:
1. Gel: Some gel and other battery types recommend lower regulation voltages and no equalization. This setting regulates to 14.0V (for a 12V battery).
2. Sealed: AGM, “maintenance free“ and some types of gel batteries. Regulates to
14.15V (12V battery) with 14.35V boost charging.
3. Flooded: Vented cells that require water to be added. Regulates to 14.4V with
14.9V and 15.1V equalizations (12V battery).