Complex sentence: Of the 1,026 convicts who embarked, 267 (256 men and 11 women) died during the voyage (26 percent); a further 486 were sick when they arrived of which 124 died soon after.
Split into simpler sentences: Of the 1,026 convicts who embarked, 267 (256 men and 11 women) died during the voyage (26%). A further 486 were sick when they arrived of which 124 died soon after.