This limit corresponds to your RRSP contribution room, which represents 18% of your income earned in the previous year or the annual contribution limit for the current year, i.e. $26,010 in 2017.
However, if you participate in an employer pension plan, your contribution room will be reduced by the amount of your pension adjustment. Usually, this represents the amount you and your employer contributed to your pension plan during the year.
If a portion of your contribution room from past years has not been used, it gets added to your contribution room for the following years.
Consult your Canada Revenue Agency notice of assessment to find out your contribution room.
Note that the Fonds de solidarité FTQ sets an annual limit of $12,500 on share subscriptions per shareholder, per calendar year, i.e. from January 1 to December 31.