Portuguese to English Art/Literary Printing & Publishing Book on sea turtle conservation

Hi everyone,

I am editing an English translation of a series of paragraphs and captions to accompany photos in a book on sea turtle conservation. My query is that in the original text, the author sometimes uses numbers (7) and sometimes writes the numbers (sete), seemingly without following any rhyme or reason. I know that it is perferable in English to write numbers unless they are long, but in this case should I maintain what's written in the text in each instance? I imagine it's more correct to write out the numbers in Portuguese too. The translator has copied the format of the original in each case. There are some examples below of cases in the text where you can see the variation between the numerals and the numbers written out. My question is whether I should leave '15' as '15' or write 'fifteen'.

"Existem sete espécies de tartarugas marinhas no mundo. Destas, cinco são encontradas em todos os oceanos do mundo, incluindo a costa do Brasil"

"As fêmeas desovam a cada dois anos, embora haja registros com intervalos entre três e quatro anos. Cada uma faz de três a cinco posturas por temporada, com intervalos médios de 15 dias, e coloca cerca de 140 ovos por ninho."

"É uma raridade poder observar a desova de uma tartaruga gigante (Dermochelys coriácea) nas areias grossas das praias próximas à foz do rio Doce. Anualmente, apenas 5 a 15 fêmeas desovam no litoral norte do Espírito Santo, a única de concentração reprodutiva regular dessa espécie no Brasil."

I was not sure how to classify this question, apologies if it would be better off on the forum. The translation is to US English. Thanks for your help!