On the General tab of the report, select the appropriate distribution. If reporting on the actual amount of the soft credit for the constituent, select Use Distribution on Gift.

Learn more about using soft credits and the soft credit distribution options (BB152).

OR

If the gift to which the soft credit is applied is split, the soft credit is also split. If you filter on a specific campaign, fund, or appeal, only that portion of the soft credit gift will show on the report. If you want the entire split gift amount to show, use all campaigns, funds, and appeals on the report.

For Example:
If a Donor makes a $100 gift and a Soft Credit Recipient receives soft credit for $50 (50% of the whole gift)
The gift is split between two funds. 
Fund A has $75
Fund B has $25

When running reports where the soft credit is to the Soft Credit Recipient using the distribution on the gift, the gift will be split matching the split on the gift and the distribution of the soft credit.
Soft Credit Recipient for Fund A would show as $37.50 because $75 is the amount of the split to Fund A and half (50%) of the entire gift is what the recipient has credit.
Soft Credit Recipient  for Fund B would show as $12.50 because $25 is the amount of the split to Fund B and half (50%) of the entire gift is what the recipient has credit.
The Total between the splits is $50, the entire amount that the Soft Credit Recipient is receiving.  If the report is only filtering on Fund A or Fund B, then the amount of the Soft Credit will not be the full $50, but the portion based on the split.