In the arrangement depicted in the figure, both springs are...

When the block is displaced by a distance $x$ from its equilibrium position, one spring gets stretched by $x$ and the other gets compressed by $x$.

The restoring force from the first spring is $F_1 = k_1 x$ in the direction opposite to the displacement.

The restoring force from the second spring is $F_2 = k_2 x$, also in the direction opposite to the displacement.

The net restoring force acting on the block is:
$F_{net} = F_1 + F_2 = k_1 x + k_2 x = (k_1 + k_2)x$

This net force acts opposite to the direction of displacement.

Using Newton's second law, the initial acceleration $a$ of the block is:
$a = \dfrac{F_{net}}{m} = \dfrac{(k_1 + k_2)x}{m}$

The direction of the acceleration is opposite to the displacement.