Fractional Factorial design changes level values

[Renger]

Using the code below I would expect a design with 8 experiments whereby the min and max levels are used for each attribute. That works and I get a design that makes sense except for one item: the levels for G2 are changed from 0.2 and 0.4 into 0 and 1. This behavior does not change when I add a middle level, if I change the order of the attributes in the design space, or if I change the name of attribute G2. It does work however, when I change the values to 2 and 4. It seems that when one of the levels is below a value of 1, that the levels are changed to 0 and 1.

My code:

from doepy import build

Define the design space

design_space = {'P_CG_substance':['P','CG'],
'P_CG_level':[1,2,3],
'AF':[1, 1.5, 2],
'MX':[1.25, 1.5, 2],
'G2':[0.2, 0.4],
}

print(design_space)

Build the design

design = build.frac_fact_res(design_space)

In the design for column P_CG_substance, replace 0 with P and 1 with CG

design['P_CG_substance'] = design['P_CG_substance'].replace({0:'P', 1:'CG'})

Print the design

print(design)

Print the number of experiments

print(f'number of experiments is {len(design)}')

Expected result:
P_CG_substance P_CG_level AF MX G2
0 P 1.0 1.0 2.00 0.4
1 CG 1.0 1.0 1.25 0.2
2 P 3.0 1.0 1.25 0.4
3 CG 3.0 1.0 2.00 0.2
4 P 1.0 2.0 2.00 0.2
5 CG 1.0 2.0 1.25 0.4
6 P 3.0 2.0 1.25 0.2
7 CG 3.0 2.0 2.00 0.4

What I get:
P_CG_substance P_CG_level AF MX G2
0 P 1.0 1.0 2.00 1.0
1 CG 1.0 1.0 1.25 0.0
2 P 3.0 1.0 1.25 1.0
3 CG 3.0 1.0 2.00 0.0
4 P 1.0 2.0 2.00 0.0
5 CG 1.0 2.0 1.25 1.0
6 P 3.0 2.0 1.25 0.0
7 CG 3.0 2.0 2.00 1.0