Is there always padding in an IMSI to make the PLMN (MCC + MNC) always 6 digits

Question

I'm wondering if I can always decode the PLMN as the first 6 digits of the IMSI, or could this potentially include the first digit of the MSIN in the case of a 2 digit MNC?

If the PLMN is always the first 6 digits, then for a 2 digit MNC is the padding between the MNC and the MSIN always 0?