what this means

The notice was issued by a co-sharer of the property, to those that are enjoying the property, stating that his request for dividing the property as per measurements and boundaries are not shared in property was not considered, and hence this notice for giving his entitled share of the properties.   This is a formal notice before filing a partition suit.  Give a suitable reply either denying the share with such reasons and engage a local advocate as the REPLY is most important and for permanent use in the stand taken by you further in court proceedings.

It mean the defendant(s) did not agree for partition by meets and bound / mutual consent.

The cause of action for instituting the suit was due to the refusal of co-sharers for an amicable partition of the co-shared property. 

This means that the plaintiff was forced to knock the doors of the court for the relief of partition which could not be done by mutual agreement among the shareholders.

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This means that the applicant (who is a co-owner/c) must have already made an amicable request for the partition of his respective share, however his co-owner denied his request as a result of which a cause of action has arose in favour of the applicant, who can now file a partition suit seeking partition of the property and being delivered his share as per proper measurement and boundaries division.