Octal numbers or base -8 uses digits from 0..7 for encoding.
Compared to binary a digit can have minimum 0 or maximum 7 as a number.

Examples:
1 = 1
7= 7
8= 10 =

27₈ = 2×8¹+7×8⁰ = 16+7 = 23₁₀

30₈ = 3×8¹+0×8⁰ = 24₁₀

4307₈ = 4×8³+3×8²+0×8¹+7×8⁰= 2247

How would you convert a 24 to base-8
Remember binary division
Divide the number by 8 until it cannot be divided
Reverse the remainders