In all measured indicators the numerator is the debt service annual amount in current US dollars. Its exact "official" definition runs as follows:
Total debt service is the sum of principal repayments and interest actually paid in foreign currency, goods, or services on long-term debt, interest paid on short-term debt, and repayments (repurchases and charges) to the IMF. Data are in current U.S. dollars.
Source : World Bank, Global Development Finance.
The Debt service / capital expenditure refers to the ratio between the debt service annual amount in current US dollars and capital expenditure during the same year. Capital expenditure is defined as follows:
Capital expenditure (% of total expenditure) is spending to acquire fixed capital assets, land, intangible assets, government stocks, and nonmilitary, nonfinancial assets. Also included are capital grants. Data are shown for central government only.
(Source : International Monetary Fund, Government Finance Statistics Yearbook and data files.)
DS/CE = Total debt service (current USD) / [(capital expenditure (% of total expenditure) / 100) • (Total expenditure (% of GDP) / 100) • GDP (current USD)]
A ratio DS/CE = 0,457 means that the debt service represents 45,7% of the capital expenditure. A ratio DS/CE = 3,487 means that the expenses due to debt service is 3,487 times more important than the capital expenditure.
Mode of interpretation: DS/CE measures the burden of the debt service in relation to public investment. It shows to what extent debt service prevents capital expenditure.