how to set following situation?

initial charge(Rate per parcel) $10
Plus rate per 100g or part thereof $1

So if customer buy an item of 300g
Total charge is $13 (1 x $10 + 3 x $1)

Thanks for your query. Please do following:

1. Under Price setting tab, Select Rate type is Weight.

I am assuming that your default weight unit is gram. If it is KG, then you will have to enter it accordingly. For example, 100 will be replaced with 0.1

Now enter following Unit Ranges:

Start . —- End . —- Cost —- per unit block —- Allow partial 
0 —- 999999 — 1 —– 100 – – — – – NO

Explanation:
——-
a. First define a big ranges 0 – 999999 so that it covers all weight
b. Per unit block ensure that it will charge $1 per 100 gram
c. Allow partial ensure that it will not charge partial block. SO it will charge $3 for 250 grams instead of $2.5

2. Under Price adjustment section, enter +10 into the field “Modifier” [+10 means it will add $10 with final cost]