At least 25% with target 25-40% of the company, with the lower end being more common for high-valuation rounds or when there’s significant dilution from earlier funding (e.g., seed rounds).
This exemplifies the need for capital journey planning and detailed pro forma cap table review, the Taylor Davidson model can help, and you may be able to advise here for mutually good outcomes. 
An area that deserves special attention on cap tables is equity allocated to incubators/accelerators, confirming this is reflective of the value added to the company and - if disproportionate work with the founders and attempt to renegotiate - prior to a priced round.