For example..
accounts receivable 160,000
less: allowance for uncollectible accounts 16,000
144,000

How to adjust accounts receivable if the estimated percentage of realizable is 70%?
..

1) 100% less 70% = 30%

2) 30% of $160,000 = $48,000

3) $48,000 less $ 16,000 = $32,000.

So, increase the allowance by $32,000.