a "12 month prison sentence" in England consists of a minimum of six months in custody followed by six months release on licence, followed by six months under supervision.
In this particular case the offender was remanded after arrest. So time on remand should be deducted from the time in prison after sentencing. Also deducted, if he's eligible, is a period on Home Detention Curfew (HDC).
HDC is available on sentences of less than four years, after 28 days of the sentence or one quarter, whichever is longer. The maximum period of HDC is 135 days.
If the offender in this case spent 2 months on remand (he was arrested in February and sentenced in April) then he would have served a further month in prison and then been released on HDC until the half way point of the sentence.
If he was released from remand before sentencing then the total time in prison for a 12 month sentence would be 3 months - inclusive of days on remand. Followed by 3 months on Home Detention Curfew.