查看Cambridge Dictionary可知，“fraction”的解释为“a number that results from dividing one whole number by another”，中文为“分数”，也就是指整数的一部分，亦可以表达为“不足整数的部分”。那么“fraction thereof”就是“fraction of a year”，整句话的意思是“每年按0.5%，不足一年的亦按0.5%”。

例句：

1. 原文：An additional charge per package for each additional HKD 800 of declared value or fraction thereof, will apply.

译文：每件包裹申报价值每多800港元（不足800港元亦按800港元计），均需支付附加费。

2. 原文：A member who suffers temporary total disability shall be entitled to 75 per cent of his daily compensation for each day or fraction thereof or temporary disability benefit not exceeding 120 days in one calendar year after exhausting all sick leave credits and collective bargaining agreement sick leave benefits, if any, but not earlier than the fourth day of his or her temporary total disability.

译文：如果投保人属于暂时完全伤残，那么每日或不足一日有权获得75%的工资，或，在用完计发福利的所有病假和集体谈判协议病假福利后（如果有的话），而在不早于其暂时完全伤残的第四天，每个日历年可按工资的一定百分比，享受不超过120天的暂时伤残福利。

3. 原文：Except during travel by sea, the daily subsistence allowance shall be paid to project personnel, at the rates and under the conditions prescribed in rule 207.16, for each calendar day or fraction thereof involving an overnight stay away from their residence during which project personnel or their family members are in official travel status, provided that for a journey of 24 hours or longer a full day's allowance at the appropriate rate shall be paid for the day on which travel is begun and that no allowance shall be paid for the day on which travel is ended.

译文：除海上旅行期间外，应于项目人员或其家属具有公务旅行身份而必须离开其住所在外过夜停留的每一日历日或不足一日历日，按照细则207.16规定的数额和条件，发给该项目人员每日生活津贴，但如行程需二十四小时或二十四小时以上，启程之日应按规定数额发放全日津贴，旅行结束之日则不发放津贴。