2826281 - P-key spent different size depending on VARCHAR size (128 or 250 bytes) -- SAP IQ

When each elements in p-key are varchar columns, depending inserted data byte length, the total used space of p-key reports different.
In real customer production system, a table with pkey of varchar(250) columns spent 84 GB, whereas varchar(128) column took 53 GB.

Below is test tables and allocation status.

pkey of t_vchar128 : Total 2512 KBytes allocated ( sp_iqindexsize )
  - inserted 10,000 rows and each column has 128 bytes data length
pkey of t_vchar250 : Total 2496 KBytes allocated
  - inserted 10,000 rows and each column has only 128 bytes data length
pkey of t2_vchar128 : Total 1584 KBytes allocated
  - inserted 10,000 rows and each column has only 10 bytes data length
pkey of t2_vchar250 : Total 2496 KBytes allocated
  - inserted 10,000 rows and each column has only 10 bytes data length

     (* t_vchar128, t_vchar250 & t2_vchar250 are similar usage. But t2_vchar128 is much different )

Questions are ,

    - There are different sizes between t2_vchar128 and other tables, What's reason for this ?
    - It seems Pkey treats CHAR or VARCHAR types to same type. Does it ? any comment will be helpful to me.

SAP IQ16.1 SP02.15

819776, pkey size, p-key, 'primary key',Varchar, , KBA , BC-SYB-IQ , Sybase IQ , How To