我的祖源有7%的日本，但我父母都没有这段祖源，请问合理吗？

{"result":[{"race_desc":"\u4e2d\u534e\u6c11\u65cf","race_en":"chinese_nation","race_probality":"0.929581","area":[{"block":"chinese_nation","race_desc":"\u5317\u65b9\u6c49\u65cf","race_en":"han_northern","race_probality":"0.504834"},{"block":"chinese_nation","race_desc":"\u5357\u65b9\u6c49\u65cf","race_en":"han_southern","race_probality":"0.243862"},{"block":"chinese_nation","race_desc":"\u901a\u53e4\u65af\u65cf\u7fa4","race_en":"tungus","race_probality":"0.064855"},{"block":"chinese_nation","race_desc":"\u7eb3\u897f\/\u5f5d\u65cf","race_en":"ny","race_probality":"0.052949"},{"block":"chinese_nation","race_desc":"\u85cf\u65cf","race_en":"tibetan","race_probality":"0.044245"},{"block":"chinese_nation","race_desc":"\u62c9\u795c\u65cf","race_en":"lahu","race_probality":"0.018050"},{"block":"chinese_nation","race_desc":"\u5176\u4ed6","race_en":"other","race_probality":"0.0010"}]},{"race_desc":"\u4e1c\u5317\u4e9a","race_en":"ne_asian","race_probality":"0.070148","area":[{"block":"ne_asian","race_desc":"\u65e5\u672c","race_en":"japanese","race_probality":"0.070128"}]},{"race_desc":"\u5176\u4ed6","race_en":"other","race_probality":"0.0004","area":[]}],"case_id":"ANCESTRY","prefix":null,"description":"\u7956\u6e90\u5206\u6790","color":null,"detail_url":"\/report2\/ancestry\/"} 附件第一个截图是我跟我妈的祖源对比。我爸爸和我爷爷基本是98%的北方汉族，第二个截图是我跟我爸的祖源对比。那么请问我7%这部分祖源到底从何而来？我姥姥已经过世了，目前无从得知。