Should be OK, but if you want to be extra safe, for 5 EUR you can buy a ticket on the another regionale to La Spezia that leaves about 20 minutes earlier, giving you another 20 minutes. Your current ticket has been prevalidated for the departure shown. You might want to stop by the station in Monterosso and see if you can take the earlier train with your current ticket. If not, then buy the new ticket to La Spezia. That one you will have to validate in the stamping machine on the platform before boarding.