If they can get within artillery firing range of the train line that goes through Tokmak, they can disrupt all rail reinforcement going to anywhere west of tokmak, which then puts the only rail reinforcement to crimea and the Kherson oblast through the long way across the Crimean bridge. M777 maximum range is 24.7km, they are 29km away, and are making steady progress. Russia knows this and is reinforcing which is making the entire front line weaker, and if Ukraine can keep up the pressure then we hopefully might be able to see something like Kharkiv happen again.