If a mass is moved up or down a distance Dh in a uniform gravitational field directed down, the change in gravitational potential energy is:

DU_g = mg Dh

We're free to define the zero for potential energy at some convenient level.

Similarly, for a charge q moving a distance Dd parallel to the field, the change in electric potential energy is:

DU_e = qE Dd

If a positive charge moves opposite to the field the change in potential energy is positive. If it moves in the direction of the field DU_e is negative. Just the opposite is true for a negative charge.

Again we're free to define the zero for potential energy at some convenient level. The value of the potential energy is not too important - what really matters is how the potential energy changes when the mass or charge moves.