Number of kun/on readings differ depending on source. WHY? Which is correct?

BIG HEADACHE. I am bummed by inconsistency of the number of kun or on readings a kanji can have according to different sources. For example, the kanji 承 has:
-according to jisho.org,6kun readings: うけたまわ.る う.ける、 こ.らす、 ささ.げる、 すく.う、 たす.ける
(to be exact:#kanji 承け - Jisho.org)

-and, according to saiga dictionaryhttp://www.saiga-jp.com/kanji_dictionary.html,1 kun reading: うけたまわ・る
( to be exact:http://www.saiga-jp.com/cgi-bin/dic.cgi ... 3741_60375)

This is just one example. Why is it so? Which one of these sources is more reliable? Or is there any unquestionably reliable online source?

PLEASE HELP.

Thank you in advance.

Click and see the pages linked each of the readings on jisho.org. こ.らす is the reading of 凝らす/懲らす not 承, ささ.げる is for 捧げる/献げる not 承, すく.う is for 巣くう/巣食う not 承,,,,,. That's Denshi Jisho's bug.

As for the reason why う.ける is not in saiga dictionary, that's because this reading is not in the Jōyō list.

Don't worry about memorising every reading for a kanji. They're not all equally common, and if something genuinely does have a lot of kun readings (e.g. 生), chances are that a number of them are limited to specific vocab words. e.g. き、for 生, I think 生地 is the only word I actually know.

In fact, on the joyo list or in some of the supplementary materials, I have seen documents which give some separation of the readings by school year - e.g. a primary school student would be expected to know 生 but not necessarily to be able to read every single word which contains 生, whereas a high school student might be expected to recognise some of the more esoteric uses, and some obscure/non-standard readings would always be given furigana if you're strictly following the joyo list.

To make your life more complicated, I'll point out that some words do not use on/kun readings (in fact, a lot of very common words are in this camp, e.g. 今日). Learn a few common/useful words which use a kanji, and you will naturally pick up the most common readings as well as the exceptions. The ones which aren't common you can leave aside until such time as you need to learn that vocab. In this case, if you're not deep into keigo/business language yet, I'd question whether learning うけたまわる should be a priority.

Toritoribe, thank you very much. It looks like a bug. I was thinking if it is because of rare pronunciations of those kanjis. Some other paper book sources that I checked stands against jisho.org, in terms of pronunciations. So any source that spinned off WWWJDIC seems to have this problem. Those are jisho.org, tangorin. They seem to give bloated number of pronunciations.

承る isn't used merely between business people. It is also used by businesses when addressing their customers. So while not an extraordinarily common kanji, it is one that any average consumer can expect to encounter in a wide variety of retail locations.