Short answer

The amount debited is higher because you pay both the clean price (shown in Arrow) and accrued interest (not shown separately) when purchasing re-issued G-bonds.

Understanding the difference

When you buy G-bonds through non-competitive bidding, you receive allotment at the weighted average rate of all competitive bidders. This rate is the clean price (excluding accrued interest), which Arrow displays as number of units owned × clean price.

RBI typically re-issues G-bonds until a substantial amount becomes outstanding. For re-issues, settlement happens at dirty price (clean price + accrued interest), even for non-competitive bidding.

When you buy an interest-bearing security between two interest payment dates, you must compensate the seller for the interest portion they earned from the last payment date to the trade date. On the next interest payment date, you will receive the full interest amount for the entire period from the previous payment date, even though you purchased the bond partway through this period. This works similarly to dividend adjustments for stocks.

Example calculation

Bond: 7.72% GS 2055 (re-issue)

Auction date: 19th October

Settlement date: 22nd October

Interest payment dates: 26th October and 26th April

Last payment date: 26th April 2018

Your bid: ₹10,000

Weighted average price (clean): 93.9

Interest payment you will receive: On 26th October: 7.72% ÷ 2 × 10,000 = ₹386 (full amount despite not holding since April)

Accrued interest calculation: RBI uses 360 days per year, 30 days per month. Formula: (Coupon rate ÷ 2) × (Days from last coupon payment ÷ 360)

Accrued interest: (7.72 ÷ 2) × (178 ÷ 360) = 1.908 (178 days = period from 26th April to 21st October)

Total amount blocked: Clean price + accrued interest: 93.9 + 1.908 = 95.808 × 100 units = ₹9,580

Amount shown in Arrow: Clean price only: 93.9 × 100 units = ₹9,390

Difference: ₹9,580 - ₹9,390 = ₹188 (this is your accrued interest payment)

You will recover this ₹188 accrued interest component in your bank account on the coupon payment date alongside your regular interest payment.