Those dimensions give a total tank volume of 54 litres, 14 US gallons and 12 imperial gallons. But the tank won't hold that much water as you have to leave a gap between the water surface and the tank rim; and decor will displace some water. I once had a tank with those dimensions I called it a 45 litre tank even though the packaging said 54 litres. 45 litres = 12 US gallons and 10 imperial gallons.
The important dimensions are 60 x 30 cm (24 x 12 inches). This is the footprint of the tank and is the same as many 60 litre tanks, just not as tall.
The important dimensions are 60 x 30 cm (24 x 12 inches). This is the footprint of the tank and is the same as many 60 litre tanks, just not as tall.