The subject is not necessary in Spanish, so both translations are perfectly correct. Most of the time, the subject will be guessed by the form under which the verb is conjugated. Moreover, in your example, the subject can be inferred without a doubt, since fui is specific for the 1st person, singular.

As for the reason why two translations are offered, it's to account the possible genders of the speaker.

Female speakers will say

Fui seguida.

Male speakers will say

Fui seguido.

The subject can be omitted in Spanish, so both translations are perfectly correct. Most of the time, the subject will be guessed by the form under which the verb is conjugated. Moreover, in your example, the subject can be inferred without a doubt, since fui is specific for the 1st person, singular.

As for the reason why two translations are offered, it's to account the possible genders of the speaker.

Female speakers will say

Fui seguida.

Male speakers will say

Fui seguido.