不好意思，请教各位前辈，我在IB收到一封英文信，应该是有关股东权益之类的，
但反复看都不是很懂，可否麻烦前辈帮忙说明一下？
信件内容如下：
This corporate action has at least one revision! To see the details, click
here
Cornerstone Total Return Fund, Inc. has announced a subscription rights
offering. Subscription rights under the symbol CRF.RTS have been issued for
effective date 2018-06-15. Rights were issued at a ratio of 1:1.
Terms of the offer are as follows:
Subscription ratio: 1 share for every 3 rights subscribed
Subscription price: the greater of (i) 107% of NAV as calculated at the close
of trading on the date of expiration of the offering and (ii) 90% of the
market price per share at expiration
CRF.RTS trading period: Not applicable
Short close out date: Not applicable
Minimum & Multiple rights required to exercise: 3 Rights
Is over-subscription available: Yes
Please note: The estimated price will be used by the Depository for
processing purposes until the final price is determined. Any difference
between the estimated and final price will be refunded or reinvested. If you
wish to have the refund reinvested please submit a ticket prior to the
expiration of the offer instructing IB to reinvest.
Rights exercises, once submitted to the depository/agent, will no longer be
eligible to be withdrawn.
Customers whose accounts are allocated a short position in the rights should
take note that the account may be held liable for the terms of the rights
offer, including any over-subscription when applicable. Liability will be
determined shortly after the end of the rights period.
IB reserves the right to perform a credit check on the basic rights
subscription request at the time of submission to the agent or depository.
Basic subscription requests will be reduced or rejected in the event the
processing of the request would result in the account being in margin deficit.
Over-subscription requests may be submitted through this election tool.
Please note, IB will accept requests to over-subscribe only in the event the
account has fully subscribed to the basic rights subscription. IB reserves
the right to perform a credit check on the over-subscription request at the
time of submission to the agent or depository. Over-subscription requests
will be reduced in the event the processing of the request would result in
the account being in margin deficit. Over-subscription requests may be
subject to pro-ration at the time of allocation based on the terms of the
offer.
Over-subscription requests must be specified in the election below as the
number of new shares you wish to purchase.
The deadline to submit instructions for exercise will be 2018-07-20 @ 11:00
(America/New York).
In the absence of an election, the subscription rights will expire worthless
and be removed from your account.
然后最后有3个选项：
1 (Default) Take no action
2 Quantity of rights to submit for exercise (Basic offer)
3 Quantity of shares to purchase through over-subscription privilege
比较有问题的是选项2、3，尤其是3，不是很清楚是什么意思。
劳烦前辈解惑了，感谢~~!