Kickstarter will only allow you to pledge for each Reward once. So if you'd like to get multiple items offered at one Reward level, simple alter your pledge amount to 2x, 3x, etc. the original pledge amount.
For example: If you'd like 2 Initials, choose Reward Level #4 and increase your pledge to $78. Before fulfillment I'll get in touch about quantities and specific designs so you'll get exactly what you need.